Method and device for rectifying regions of a fisheye view image - Patent Application 20070122997

Abstract

To provide a method for dewarping a region of a fisheye view image and an electronic device.SOLUTION: A method comprises: defining a region of interest ROI within a fisheye view image, determining a center G of the ROI; defining a temporary annulus sector region of the fisheye view image such that the temporary annulus sector region comprises the ROI, and such that the temporary annulus sector region has its center at a first dewarping pole DP1 and has a temporary outer arc shaped edge and a temporary inner arc shaped edge; defining a second dewarping pole DP2 in the fisheye view image at a dewarping pole moving distance D from DP1 along a radial direction extending from the center G of the ROI through the DP1; setting a dewarping annulus sector region of the fisheye view image such that the dewarping annulus sector region comprises the ROI, and such that the dewarping annulus sector region has its center at DP2 and has its dewarping inner arc shaped edge maintained at a same radial distance from DP1 as the temporary inner arc shaped edge; and dewarping the dewarping annulus sector region of the fisheye view image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY The present disclosure resides in a method and device for rectifying regions of a fisheye view image. [Background technology]

[0002] A fisheye view image is an image with a wide field of view. Such a fisheye view image is captured by a fisheye lens to monitor the surrounding environment. Naturally, however, the fisheye view image is distorted due to the wide-angle imaging of the surrounding environment, which obscures object features of objects in the image, with the degree of distortion depending on the location in the fisheye view image. To unambiguously obscure object features, the fisheye view image may be rectified to at least partially recover the true geometry of the object. While rectifying regions in a fisheye view image is known to those skilled in the art, there is a need for an improved approach for rectifying regions of a fisheye view image such that object features in the rectified regions remain more amenable to human visualization and, possibly, to the application of object detection, object classification, and / or object recognition algorithms to the object features in the rectified regions. Summary of the Invention

[0003] It is therefore an object of the present invention to provide an improved approach for rectifying regions of a fisheye view image.

[0004] According to a first aspect, there is provided a computer-implemented method for rectifying a region of a fisheye-view image, where the fisheye-view image is captured by a fisheye lens camera and includes a first rectification pole DP1. The method comprises: defining a region of interest ROI in the fisheye view image; Determining the center G of the ROI; defining a temporary annular sector region of the fisheye view image, the temporary annular sector region including the ROI, the temporary annular sector region having a center at DP1 and having a temporary outer arc-shaped edge and a temporary inner arc-shaped edge; defining a second distortion correction pole DP2 in the fisheye view image at a distortion correction pole movement distance D along a radial direction extending from G of the ROI through DP1; setting a distortion-corrected annular sector region of the fisheye view image such that the distortion-corrected annular sector region includes the ROI, the distortion-corrected annular sector region having its center at DP2 and its distortion-corrected inner arc-shaped edge maintained at the same radial distance from DP1 as the temporary inner arc-shaped edge; Distortion correction of the circular sector area of ​​the fisheye view image Includes:

[0005] The ROI may contain an object used in an object detection, object classification, and / or object recognition algorithm. The algorithm(s) may be performed after the ROI is rectified, thereby providing a less distorted image on which the algorithm(s) are performed. Thus, the algorithm(s) may be more robust.

[0006] Additionally, the distortion-corrected image may be easier for humans to visualize when viewing the image or a video stream of images.

[0007] Furthermore, the present disclosure may provide a computationally efficient approach for rectifying portions of a fisheye view image, which may enable accurate object detection, classification, and / or recognition performed in real time, thus saving computation time and power.

[0008] The distortion correction annular sector region may be configured such that its distortion correction outer arc edge is maintained at the same radial distance from DP1 as the temporary outer arc edge, thus providing efficient configuration of the distortion correction outer arc edge, which may save processing time and / or processing power.

[0009] The method may further include calculating D to be equal to the radial distance R between G of the ROI and point P1 on the edge of the fisheye-view image, such that DP2, G, and P1 lie on the same straight line, where G is located between DP2 and P1. This preserves symmetry between the temporary annular sector area and the distortion-corrected annular sector area, thereby facilitating efficient distortion correction of the ROI. Thus, again, processing time and / or processing power may be saved.

[0010] This method calculates D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, so that DP2, G, and P1 are placed on the same straight line, where G is placed between DP2 and P1, and the tolerance of the distortion correction polar movement distance D is the radial extension R of the ROI. ROI may be RR ROI <D<R+R ROI The method may further include causing the

[0011] This may provide flexibility to the method.

[0012] The definition of DP2 is calculating a temporary arc rate, the length of the temporary outer arcuate edge divided by the length of the temporary inner arcuate edge, or the length of the line segment joining the first and second end points of the temporary outer arcuate edge divided by the length of the line segment joining the first and second end points of the temporary inner arcuate edge; Calculating by either comparing the temporary arc rate to a threshold arc rate; if the temporary arc ratio exceeds the threshold arc ratio, then calculating D by determining that the distortion-corrected arc ratio is less than or equal to the threshold arc ratio, the length of the outer arcuate edge of the distortion correction divided by the length of the inner arcuate edge of the distortion correction, or the length of the line segment joining the first and second end points of the outer arcuate edge of the distortion correction divided by the length of the line segment joining the first and second end points of the inner arcuate edge of the distortion correction; Calculation is performed by either may include:

[0013] This allows for fast and accurate position calculations of the DP2, which may save processing time and / or power.

[0014] Correcting the distortion-corrected annular sector region of the fisheye view image includes calculating, by a coordinate transformation, a transformation from a representation of the spherical coordinates of the distortion-corrected annular region to a projection of a representation of the rectilinear coordinates of the distortion-corrected annular region, such that the distortion-corrected annular sector region is an equirectangular projection of the fisheye view image.

[0015] The threshold arc ratio may be a set of threshold arc ratios, where each threshold arc ratio of the set of threshold arc ratios belongs to a particular annular region of the field of view FOV of the fisheye lens camera. Because fisheye-view images are generally associated with a position-dependent degree of distortion, different regions of the fisheye-view image associated with different threshold arc ratios may improve accurate distortion correction for each region, thereby facilitating object detection.

[0016] According to a second aspect, there is provided a non-transitory computer-readable storage medium having stored thereon instructions which, when executed on a device having processing capability, perform the method according to the first aspect.

[0017] The above-mentioned features and advantages of this method, where applicable, apply equally to this second aspect, and in order to avoid unnecessary repetition, please see above.

[0018] According to a third aspect, there is provided an electronic device comprising a circuit, the circuit comprising: a region of interest (ROI) definition function configured to define an ROI within the fisheye view image; a center determination function configured to determine a center of the ROI; a temporary annular sector region definition function configured to define a temporary annular sector region of the fisheye-view image, such that the temporary annular sector region includes the ROI, such that the temporary annular sector region has a center at the first distortion correction pole DP1 of the fisheye-view image and has a temporary outer arc-shaped edge and a temporary inner arc-shaped edge; a distortion correction pole definition function configured to define a second distortion correction pole DP2 in the fisheye view image at a distortion correction pole movement distance D along a radial direction extending from G of the ROI through DP1; a distortion correction annular sector area setting function configured to set a distortion correction annular sector area of ​​the fisheye view image such that the distortion correction annular sector area includes the ROI, such that the distortion correction annular sector area has its center at DP2 and has its distortion correction inner arc-shaped edge maintained at the same radial distance from DP1 as the temporary inner arc-shaped edge; a distortion correction function configured to correct a corrected annular sector region of the fisheye view image; is configured to run

[0019] The above features and advantages of this method, where applicable, apply equally to this third aspect, and in order to avoid unnecessary repetition, please see above.

[0020] The distortion correction annular sector area setting function may include a shifting function configured to set the distortion correction annular sector area so that the outer arcuate edge of the distortion correction is maintained at the same radial distance from DP1 as the temporary outer arcuate edge.

[0021] The circuit may be further configured to perform a distance calculation function configured to calculate D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, such that DP2, G, and P1 lie on the same straight line, where G is located between DP2 and P1.

[0022] The distortion correction pole definition function calculates D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, so that DP2, G, and P1 are located on the same straight line, where G is located between DP2 and P1, and the radial extension R of the ROI is calculated by a distance calculation function configured to calculate D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, so that DP2, G, and P1 are located on the same straight line, where G is located between DP2 and P1. ROI Including the tolerance of the distortion correction pole travel distance D, RR ROI <D<R+R ROI The method may be further configured to ensure that:

[0023] The distortion correction polar definition function A temporary arc ratio calculation function, which calculates the temporary arc ratio by: the length of the temporary outer arcuate edge divided by the length of the temporary inner arcuate edge, or the length of the line segment joining the first and second end points of the temporary outer arcuate edge divided by the length of the line segment joining the first and second end points of the temporary inner arcuate edge; A temporary arc ratio calculation function configured to calculate the arc ratio by one of the following: a comparison function configured to compare the temporary arc rate to a threshold arc rate; an arc-ratio condition function configured to calculate D by requiring the distortion-corrected arc-ratio to be less than or equal to the threshold arc-ratio if the temporary arc-ratio exceeds the threshold arc-ratio, wherein the distortion-corrected arc-ratio is the length of the outer arcuate edge of the distortion correction divided by the length of the inner arcuate edge of the distortion correction, or the length of the line segment joining the first and second end points of the outer arcuate edge of the distortion correction divided by the length of the line segment joining the first and second end points of the inner arcuate edge of the distortion correction; The arc rate condition function is calculated by either may include:

[0024] The fisheye lens image may be an iso-rectangular projection of an environment including the distortion-corrected annular region, wherein the distortion correction function is further configured to calculate a transformation from the iso-rectangular projection of the distortion-corrected annular region to a rectilinear projection of the distortion-corrected annular region by a coordinate transformation.

[0025] In general, all terms used in the claims are to be interpreted according to their ordinary meaning in the art unless expressly defined herein. Any reference to "a / an / the [element, device, component, means, step, etc.]" is openly interpreted as a reference to at least one instance of that element, device, component, means, step, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless expressly stated.

[0026] The above and further objects, features, and advantages of the present invention will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments, taken in conjunction with the accompanying drawings, in which like reference numerals are used to refer to similar components, in which: [Brief explanation of the drawings]

[0027] [Figure 1]1 shows a flowchart of a method for rectifying a region in a fisheye view image. [Figure 2] 1 shows a schematic diagram of a fisheye view image. [Figure 3] 10A and 10B illustrate schematic diagrams of undistorted polar shifting of a fisheye view image; [Figure 4] 10A and 10B show schematic diagrams illustrating further details relating to the definition of a second distortion correction pole for a fisheye view image; [Figure 5] 10A and 10B illustrate schematic diagrams of tolerances for undistortion polar shifts of fisheye view images; [Figure 6] Further details are given on how to calculate the undistortion polar shift of the fisheye view image. [Figure 7] 1 shows a schematic representation of an electronic device in which the disclosed method may be implemented; DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will now be described in more detail with reference to the accompanying drawings, which illustrate presently preferred embodiments of the invention. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth below. Rather, these embodiments are provided for completeness and completeness, and to fully convey the scope of the invention to those skilled in the art.

[0029] FIG. 1 schematically illustrates a flowchart of an example method 100 for correcting a region of a fisheye-view image 200, where the fisheye-view image is captured by a fisheye lens camera and includes a first distortion correction pole DP1. DP1 may be the optical center of the fisheye-view image 200. However, as will be readily understood by those skilled in the art, DP1 may similarly be set according to other criteria. FIG. 1 may be conveniently viewed in conjunction with FIGS. 2 and 3 below. The fisheye-view image 100 may be captured by a camera having mounted thereon any suitable type of fisheye lens, such as, for example, a circular APS-C type, a full-frame APS-C type, a zoom APS-C type, a circular type, a full-frame type, or a zoom type. Preferably, the raw data of the fisheye-view image 200 is such that the edges of a set of active pixels form a substantially circular geometry, and the first distortion correction pole DP1 can be viewed as the origin of the polar coordinate system of the fisheye-view image. Thus, any pixel in the fisheye-view image 200 may be associated with polar coordinates, thereby having a radial and an angular variable. The polar coordinate system may equivalently be represented in the complex plane. Note that rectifying the fisheye-view image 200 generally requires considering spherical coordinates, i.e., the additional angular variable, to be rectified onto the iso-rectangular projection. This is explained further below.

[0030] The method 100 includes defining 110 a region of interest (ROI) in the fisheye-view image 200. The ROI may be obtained from an image segmentation algorithm, an edge detection algorithm, or the like applied to the fisheye image 200. The ROI may include an object in the fisheye-view image 200. By way of example, the ROI may include a car, a truck, a person, or the like. The ROI preferably substantially encompasses the edge of the object, such as the car, truck, or person, and may optionally be subsequently processed in an object detection, object classification, and / or object recognition algorithm. Preferably, the ROI entirely encompasses the edge of the object. Alternatively, the ROI may include multiple nearby objects. Examples of these are a group of people, a biker, or the like. The same may be true for an ROI that includes multiple nearby objects. That is, such an ROI may substantially encompass the edges of multiple nearby objects. In the analogy of a group of people, this may imply that the group of people may possibly be encapsulated by a polygon that has been optimized to minimize the area of ​​the ROI.

[0031] The method 100 further includes determining 120 a center G of the ROI. G can be calculated, or at least predicted, using any calculation method, such as a method based on the pixels encompassed by the edge of the ROI and the positions of those pixels. The center G may be the centroid of the ROI. Alternatively, the center G may be the center of a temporary annular sector region 210, which will be described further below. In such a situation, the center G may be located on a radially and angularly centered point of the temporary annular sector region 210. Alternatively, if the ROI is defined in a coordinate system having radial and angular coordinates associated therewith, the radial coordinate of the center G may be the average value of the ROI's maximum radial extension, and the angular coordinate of the center G may be the average value of the ROI's maximum angular extension. Note that if the center G is the ROI's centroid, the center G may be located outside the ROI's edge if the ROI has a highly irregular geometry. The same may be true for alternative procedures for determining the center G.

[0032] This method 100 further includes defining a temporary annular sector region 210 of the fisheye view image 200 such that the temporary annular sector region 210 includes the ROI, the temporary annular sector region 210 has its center at DP1, and has a temporary outer arc-shaped edge 212 and a temporary inner arc-shaped edge 214. The temporary annular sector region 210 may be a substantially mathematical annular sector region. Thus, the outer arc-shaped edge 212 may be associated with a first circle, the inner arc-shaped edge 214 may be associated with a second circle, and the first and second circles have different radii r1, r2. The ratio between these radii may fall within the range of 0.9 < r1 / r2 < 1.1. Preferably, r1 / r2 is a number relatively close to 1 such that 0.98 < r1 / r2 < 1.02.

[0033] This method 100 further includes defining a second distortion correction pole DP2 in the fisheye view image 200 along a distortion correction pole movement distance D along the radial direction extending from DP1 through DP1 to G of the ROI. This radial direction thus substantially coincides with the radial variable of the polar coordinate system of the fisheye view image 100. This radial direction is further directed such that DP1 is positioned between DP2 and G. This is schematically shown in FIG. 3.

[0034] This method 100 further includes setting a distortion correction annular sector region 310 of the fisheye view image 200 such that the distortion correction annular sector region 310 includes the ROI, and the distortion correction annular sector region 310 has its center at DP2 and has an inner arcuate edge of the distortion correction that is maintained at the same radial distance r1 from DP1 as the temporary inner arcuate edge. However, the shape of the inner arcuate edge 314 of the distortion correction is different from the inner arcuate edge 214. This is because the radius of curvature of the inner arcuate edge 314 of the distortion correction is larger than the radius of curvature of the inner arcuate edge 214 after defining the second distortion correction pole DP2. Conversely, the radius of curvature of the outer arcuate edge 312 of the distortion correction is larger than the radius of curvature of the outer arcuate edge 212 after defining the second distortion correction pole DP2. The fisheye view image radius R1 of the circular edge 202 of the fisheye view image 200 may be different from the radius R2 of the second circle 302 having the second distortion correction pole DP2 as its center. Preferably, the radii R1 and R2 have similar magnitudes. For illustrative purposes, the ratio between those radii may fall within the range of 0.9 < R1 / R2 < 1.1. Note that the shape and scale of the ROI are similar before and after the movement of the distortion correction pole.

[0035] This method 100 further includes distortion-correcting 160 the distortion correction annular sector region 310 of the fisheye view image 200. Distortion-correcting 160 may be performed using any suitable transformation algorithm for distortion correction between the coordinate system of the fisheye view image and any coordinate system. Preferably, the any coordinate system is a Cartesian coordinate system to substantially recover the distortion-free geometry of the ROI if the second distortion correction pole DP2 is properly placed as described above. The substantially recovered distortion-free geometry of the ROI may subsequently be used, for example, in object detection, classification, and / or recognition algorithms.

[0036] The distortion correction annular sector region 310 may be configured such that its distortion correction outer arcuate edge 312 is maintained at the same radial distance from DP1 as the temporary outer arcuate edge 212. Thus, r2 and r3 in Figures 2 and 3 may be substantially similar, which implies that the area of ​​the distortion correction annular sector region 310 is smaller than the area of ​​the temporary annular sector region 210.

[0037] The movement and details of the distortion correction pole of the ROI are further highlighted in relation to Figure 4. The method 100 may further include calculating D to be equal to the radial distance R between G of the ROI and point P1 on the edge 202 of the fisheye view image 200, such that DP2, G, and P1 lie on the same straight line L1, where G is located between DP2 and P1.

[0038] The tolerance of the distortion correction polar movement distance D is the radial extension R of the ROI. ROI and RR ROI <D<R+R ROI This is shown diagrammatically in Figure 5. Thus, the distortion correction outer arcuate edge 312 is maintained at the same radial distance from DP1 as the temporary outer arcuate edge 212, and the distortion correction polar movement distance is D+d, where d is 0 <d<R ROI However, a suitable distortion correction polar shift distance is, for example, the distortion correction polar shift distance D in FIG. 4. A case where the distortion correction polar shift distance is greater than D is shown in FIG. 5, where the second circle 302 is larger than the circular edge 202 of the fisheye-view image 200. The accuracy of distortion correction depends on the distortion correction polar shift distance D of the ROI, the radial extension R of the fisheye-view image relative to the radius R1. ROI , and possibly the radial position of G of the ROI, for example if the ROI has a fairly irregular geometry in the fisheye view image 200.

[0039] With reference to FIG. 6 , further details of how to define the second distortion correction pole DP2 are shown. Defining DP2 may include, in a first calculation procedure, calculating a temporary arc ratio by the length AL1 of the temporary outer arc edge 212 divided by the length AL2 of the temporary inner arc edge 214. See FIG. 6(i). Alternatively, in a second calculation procedure, the temporary arc ratio may be calculated by the length LL1 of the line segment LL1 connecting the first and second end points of the temporary outer arc edge 212 divided by the length LL2 of the line segment LL2 connecting the first and second end points of the temporary inner arc edge 214. See FIG. 6(ii). Note that the above first and second calculation procedures yield similar ratios. Defining DP2 may further include comparing the temporary arc ratio to a threshold arc ratio. If the temporary arc ratio exceeds the threshold arc ratio, D may be calculated by requiring the distortion-corrected arc ratio to be less than or equal to the threshold arc ratio. The distortion-corrected arc ratio is calculated similarly to the temporary arc ratio, that is, by the length AL3 of the distortion-corrected outer arc edge 312 divided by the length AL4 of the distortion-corrected inner arc edge 314. See FIG. 6(iii). Alternatively, the distortion-corrected arc ratio may be calculated by the length LL3 of the line segment LL3 connecting the first and second end points of the distortion-corrected outer arc edge 312 divided by the length LL4 of the line segment LL4 connecting the first and second end points of the distortion-corrected inner arc edge 314. See FIG. 6(iv). Again, note that these calculation procedures yield similar ratios. Once the arc lengths of the outer arc edge 312 of the distortion correction and the inner arc edge 314 of the distortion correction are calculated, a second distortion correction pole DP2 common to these arcs can be easily obtained. Alternatively, the position of the second distortion correction pole DP2 can be calculated iteratively. In such a situation, DP2 may be initially placed randomly or by a suitable assumption, and then the arc ratio is calculated. If the arc ratio is outside the threshold arc ratio, the position of DP2 is updated accordingly. This update may be performed using any suitable technique, such as using a Monte Carlo method.

[0040] Correcting 160 the distortion-corrected annular sector region 310 of the fisheye-view image 200 may include calculating, via a coordinate transformation, a transformation from a representation of spherical coordinates of the distortion-corrected annular region to a representation of rectilinear coordinates of the distortion-corrected annular region 310. The distortion-corrected annular sector region 310 may thereby be viewed as an iso-rectangular projection of the fisheye-view image 200.

[0041] Projecting a spherical image onto a two-dimensional sheet / screen induces image distortion, where the degree of local image distortion depends on the location of a particular image region in the spherical image. For example, mapping the spherical, two-dimensional surface of the Earth onto a flat, two-dimensional surface induces local image distortion that is inversely proportional to the distance to the North or South Pole, while the local distortion is minimal near the equator. For illustrative purposes, the apparent area of ​​Antarctica in such projections is often over-mapped relative to continents located near the equator, such as Africa or Central America. That is, the real-world area ratio between Antarctica and Africa is significantly different compared to two-dimensional representations of those continents. Therefore, depending on the location of the geometric poles, certain locations on the spherical image may be configured to experience minimal distortion. Shifting the location of the geometric poles may thereby reduce local distortion at certain locations while simultaneously increasing local distortion at other locations. In other words, the first distortion correction pole DP1 of the fisheye-view image 200 may be viewed as the geometric pole when representing the fisheye-view image 200 by a hemisphere in a spherical coordinate system, and the definition of the second distortion correction pole DP2 may be viewed as thereby shifting the geometric pole to reduce local distortion of the ROI.

[0042] 7, there is shown, in a highly schematic manner, an electronic device 400 on which the above-described method 100 may be implemented. Some features of the electronic device 400 have already been described in relation to this method above; to avoid unnecessary repetition, reference is made to the above, where applicable.

[0043] The electronic device 400 may include a device 410 for capturing an image of a digital representation of the physical structure of an environment. This device may be, for example, a typical ceiling- or wall-mounted digital camera including an imaging sensor. The electronic device 400 may further include a fisheye lens 412 for providing the fisheye view image 200. The fisheye lens 412 may be of any type, as described above. The electronic device 400 further includes a circuit 420. The circuit 420 is configured to perform a region of interest (ROI) definition function 421 configured to define an ROI within the fisheye view image 200. The circuit 420 is further configured to perform a center determination function 422 configured to determine a center G of the ROI. The circuit 420 is further configured to execute a temporary annular sector region definition function 423 configured to define a temporary annular sector region 210 in the fisheye-view image 200 such that the temporary annular sector region 210 includes the ROI, the temporary annular sector region 210 having its center at a first distortion correction pole DP1 in the fisheye-view image 200, and having a temporary outer arcuate edge 212 and a temporary inner arcuate edge 214. The circuit 420 is further configured to execute a distortion correction pole definition function 424 configured to define a second distortion correction pole DP2 in the fisheye-view image 200 at a distortion correction pole travel distance D along a radial direction extending from G of the ROI through DP1. The circuit 420 is further configured to execute a distortion correction annular sector region setting function 425 configured to set the distortion correction annular sector region 310 of the fisheye-view image 200 such that the distortion correction annular sector region 310 includes the ROI, such that the distortion correction annular sector region 310 has its center at DP2 and has its distortion correction inner arc-shaped edge 314 maintained at the same radial distance R1 from DP1 as the temporary inner arc-shaped edge 214. The circuit 420 is further configured to execute a distortion correction function 426 configured to correct the distortion correction annular sector region 310 of the fisheye-view image 200.

[0044] The distortion correction annular sector area setting function 425 may include a shifting function configured to set the distortion correction annular sector area 310 so that its distortion correction outer arc edge 312 is maintained at the same radial distance from DP1 as the temporary outer arc edge 212.

[0045] The circuit 420 may further be configured to perform a distance calculation function configured to calculate D to be equal to the radial distance R between G of the ROI and a point P1 on the edge 202 of the fisheye view image, such that DP2, G, and P1 lie on the same straight line L1, where G is located between DP2 and P1.

[0046] The distortion correction pole definition function 424 calculates D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, so that DP2, G, and P1 lie on the same straight line L1, where G lies between DP2 and P1, and calculates the radial extension R of the ROI by a distance calculation function configured to calculate D to be equal to the radial distance R between G of the ROI and a point P1 on the edge of the fisheye view image, so that DP2, G, and P1 lie on the same straight line L1, where G lies between DP2 and P1. ROI Including the tolerance of the distortion correction polar travel distance D, RR ROI <D<R+R ROI The method may be further configured to ensure that:

[0047] The distortion correction pole definition function 424 may include a temporary arc-ratio calculation function configured to calculate the temporary arc-ratio as either the length AL1 of the temporary outer arc-shaped edge 212 divided by the length AL2 of the temporary inner arc-shaped edge 214, or the length LL1 of the line segment LL1 connecting the first and second end points of the temporary outer arc-shaped edge 212 divided by the length LL2 of the line segment LL2 connecting the first and second end points of the temporary inner arc-shaped edge 214. The distortion correction pole definition function 424 may further include a comparison function configured to compare the temporary arc-ratio to a threshold arc-ratio. The distortion correction pole definition function 424 may further include an arc-ratio condition function configured to, if the temporary arc-ratio exceeds the threshold arc-ratio, calculate D by requiring that the distortion-corrected arc-ratio be less than or equal to the threshold arc-ratio. The distortion correction arc ratio may be calculated as either the length AL3 of the distortion correction outer arc edge 312 divided by the length AL4 of the distortion correction inner arc edge 314, or the length LL3 of the line segment connecting the first and second end points of the distortion correction outer arc edge 312 divided by the length LL4 of the line segment connecting the first and second end points of the distortion correction inner arc edge 314.

[0048] The distortion correction function 426 may be further configured to calculate a coordinate transformation from a representation of spherical coordinates of the distortion-corrected annular sector region 310 to a representation of rectilinear coordinates of the distortion-corrected annular sector region 310, such that the distortion-corrected annular sector region is an equirectangular projection of the fisheye view image 200.

[0049] Other features and embodiments of this electronic device may be applicable to the above description of this method 100.

[0050] Those skilled in the art will understand that the present invention is by no means limited to the preferred embodiments described above, but on the contrary, many modifications and variations are possible within the scope of the claims.

[0051] Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Claims

1. 1. A computer-implemented method (100) for rectifying a region of a fisheye-view image (200), the fisheye-view image (200) being captured by a fisheye lens camera and including a first rectification pole (DP1); Defining (110) a region of interest (ROI) within the fisheye view image (200); determining (120) the center (G) of the ROI; defining (130) a temporary annular sector region (210) of the fisheye-view image (200), the temporary annular sector region (210) including the ROI, the temporary annular sector region (210) having a center at DP1 and a temporary outer arcuate edge (212) and a temporary inner arcuate edge (214); defining (140) a second distortion correction pole (DP2) in the fisheye-view image (200) along a radial direction extending from DP1 through DP1 to G of the ROI a distortion correction pole movement distance (D), wherein the radial direction is further oriented such that DP1 is located between DP2 and G; setting (150) a distortion-corrected annular sector region (310) of the fisheye-view image (200), the distortion-corrected annular sector region (310) including the ROI, the distortion-corrected annular sector region (310) having its center at DP2, and a distortion-corrected inner arc-shaped edge (314) of the distortion-corrected annular sector region (310) maintained at the same radial distance (r1) from DP1 as the temporary inner arc-shaped edge (214) along the radial direction extending from G of the ROI through DP1; Distortion correcting (160) the distortion-corrected circular sector region (310) of the fisheye-view image (200); A method (100) comprising:

2. 2. The method of claim 1, wherein the distortion correction annular sector region (310) is set such that its distortion correction outer arc edge (312) is maintained at the same radial distance (r2) from DP1 as the temporary outer arc edge (212) along the radial direction extending from G of the ROI through DP1.

3. 2. The method of claim 1, further comprising calculating D to be equal to the radial distance (R) between G of the ROI and a point (P1) on the edge of the fisheye view image (200), such that DP2, G, and P1 lie on the same straight line (L1), where G is located between DP2 and P1.

4. D, R-R ＲＯＩ <D<R+R ＲＯＩ and further calculating: where R is the radial distance between G of the ROI and a point (P1) on the edge of the fisheye view image (200), such that DP2, G, and P1 are located on the same straight line (L1), where G is located between DP2 and P1; R ＲＯＩ 2. The method of claim 1, wherein ∑ is a radial extension indicating a tolerance of the distortion correction polar travel distance (D).

5. The definition of DP2 is calculating a temporary arc rate, the length (AL1) of the temporary outer arcuate edge (212) divided by the length (AL2) of the temporary inner arcuate edge (214); or the length (LL1) of the line segment joining the first and second end points of the temporary outer arcuate edge (212) divided by the length (LL2) of the line segment joining the first and second end points of the temporary inner arcuate edge (214); Calculating by either comparing the temporary arc rate to a threshold arc rate; if the temporary arc ratio exceeds the threshold arc ratio, then calculating D by determining when the distortion-corrected arc ratio is less than or equal to the threshold arc ratio; wherein the distortion-corrected arc ratio is the length (AL3) of the outer arcuate edge (312) of the distortion correction divided by the length (AL4) of the inner arcuate edge (314) of the distortion correction, or the length (LL3) of the line segment joining the first and second end points of the outer arcuate edge (312) of the distortion correction divided by the length (LL4) of the line segment joining the first and second end points of the inner arcuate edge (314) of the distortion correction; The method of claim 1, wherein the calculation is performed by either

6. The rectifying (160) of the rectified circular sector region (310) of the fisheye-view image (200) is performed by a coordinate transformation of: Calculating a transformation from a representation of spherical coordinates of the distortion-corrected circular sector area (310) to a representation of rectilinear coordinates of the distortion-corrected circular sector area (310).

2. The method of claim 1, wherein the distortion-corrected annular sector region (310) is thereby an equi-rectangular projection of the fisheye-view image (200).

7. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed on a device having processing capabilities, perform the method (100) of any one of claims 1 to 6.

8. An electronic device (400) including a circuit (420), the circuit (420) comprising: a region of interest (ROI) definition function (421) configured to define an ROI within the fisheye view image (200); a center determination function (422) configured to determine the center (G) of the ROI; a temporary annular sector region definition function (423) configured to define a temporary annular sector region (210) of the fisheye-view image (200) such that the temporary annular sector region (210) includes the ROI, and such that the temporary annular sector region (210) has a center at a first distortion correction pole (DP1) of the fisheye-view image (200) and has a temporary outer arc-shaped edge (212) and a temporary inner arc-shaped edge (214); a distortion correction pole definition function (424) configured to define a second distortion correction pole (DP2) in the fisheye-view image (200) from DP1 along a radial direction extending from G of the ROI through DP1 at a distortion correction pole movement distance (D), wherein the radial direction is further oriented such that DP1 is located between DP2 and G; a distortion correction annular sector area setting function (425) configured to set a distortion correction annular sector area (310) of the fisheye-view image (200) such that the distortion correction annular sector area (310) includes the ROI, and such that the distortion correction annular sector area (310) has its center at DP2, and a distortion correction inner arc-shaped edge (314) of the distortion correction annular sector area (310) is maintained at the same radial distance (r1) from DP1 as the temporary inner arc-shaped edge (214) along the radial direction extending from G of the ROI through DP1; a distortion correction function (426) configured to correct the distortion of the corrected circular sector region (310) of the fisheye-view image (200); An electronic device (400) configured to execute the

9. 9. The electronic device of claim 8, wherein the distortion correction annular sector area setting function includes a shifting function configured to set the distortion correction annular sector area such that its distortion correction outer arc edge is maintained at the same radial distance r2 from DP1 as the temporary outer arc edge 212 along the radial direction extending from G of the ROI through DP1.

10. 10. The electronic device (400) of claim 8 or 9, wherein the circuit (420) is further configured to perform a distance calculation function configured to calculate D to be equal to the radial distance (R) between G of the ROI and a point (P1) on the edge of the fisheye view image (200), such that DP2, G, and P1 are located on the same straight line (L1), where G is located between DP2 and P1.

11. The distortion correction pole definition function defines D as: R-R ＲＯＩ <D<R+R ＲＯＩ and further configured to calculate such that where R is the radial distance (R) between G of the ROI and a point (P1) on the edge (202) of the fisheye view image (200), and DP2, G, and P1 are located on the same straight line (L1); R ＲＯＩ 10. The electronic device (400) of claim 8 or 9, wherein is a radial extension indicating a tolerance of the distortion correction polar travel distance (D).

12. The distortion correction pole definition function (424) A temporary arc ratio calculation function, which calculates the temporary arc ratio by: the length (AL1) of the temporary outer arcuate edge (212) divided by the length (AL2) of the temporary inner arcuate edge (214); or the length (LL1) of the line segment joining the first and second end points of the temporary outer arcuate edge (212) divided by the length (LL2) of the line segment joining the first and second end points of the temporary inner arcuate edge (214); A temporary arc ratio calculation function configured to calculate the arc ratio by one of the following: a comparison function configured to compare the temporary arc rate with a threshold arc rate; an arc-ratio condition function configured to calculate D by requiring a distortion-corrected arc-ratio to be less than or equal to the threshold arc-ratio if the temporary arc-ratio exceeds the threshold arc-ratio, wherein the distortion-corrected arc-ratio is the length (AL3) of the outer arcuate edge (312) of the distortion correction divided by the length (AL4) of the inner arcuate edge (314) of the distortion correction, or the length (LL3) of the line segment joining the first and second end points of the outer arcuate edge (312) of the distortion correction divided by the length (LL4) of the line segment joining the first and second end points of the inner arcuate edge (314) of the distortion correction; An arc rate condition function calculated by either 10. The electronic device (400) of claim 8 or 9, comprising:

13. 10. The electronic device of claim 8, wherein the distortion correction function is further configured to calculate a coordinate transformation from a representation of spherical coordinates of the distortion-corrected annular sector region to a representation of rectilinear coordinates of the distortion-corrected annular sector region, whereby the distortion-corrected annular sector region is an equi-rectangular projection of the fisheye view image.

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