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A video image and image technology, which is applied in the field of airborne video display, can solve problems such as slow processing speed, large buffer areas, and holes in rotating images, and achieve the effects of being suitable for hardware implementation, reducing buffer space, and improving real-time performance
Inactive Publication Date: 2014-05-28
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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The advantage of the forward rotation mapping method is that it can be mapped to the rotated coordinates only by knowing the current pixel value and its coordinates, and the real-time performance is very high; the disadvantage is that since the floating point coordinates are obtained after rotation, and the image coordinates are the whole point, It will cause multiple pre-rotation coordinates to correspond to the same post-rotation coordinate, and some post-rotation coordinates do not have corresponding pre-rotation coordinates, making the rotated image appear "hole" phenomenon
The advantage of the reverse rotation mapping method is that the coordinates obtained after the reverse rotation of the coordinates after rotation, except th
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[0045] Example one
[0046] In this embodiment, the video image is rotated counterclockwise by θ°, where 0 <θ≤45. Use the coordinates of the jth and j+1th rows before rotation to obtain the corresponding video rotation processing result.
[0047] Figure 2a Is a schematic diagram of forward rotation mapping, assuming that the image coordinates before rotation are (x 1 ,y 1 ), each pixel of each line of image around the center of the screen (x 0 ,y 0 ) After rotating the angle θ counterclockwise, the rotated image coordinates are (x 1 ',y 1 '). The formula is:
[0048] x 1 ′ = ( x 1 - x 0 ) cos θ - ( y 1 - y 0 ) sin θ + x 0 y 1 ′ = ( x 1 - x 0 ) sin θ + ( y 1 - y 0 ) cos θ + y 0
[0049] Forward the first and last coordinates (1, j), (cols, j) of the j-th row to the corresponding rotated floating-point coordinates (x s ,y s ),(x e ,y...
Example Embodiment
[0063] Embodiment two
[0064] In this embodiment, the video image is rotated counterclockwise by θ°, where -45≤θ <0. Use the coordinates of the jth and j+1th rows before rotation to obtain the corresponding video rotation processing result.
[0065] Forward the first and last coordinates (1, j), (cols, j) of the j-th row to the corresponding rotated floating-point coordinates (x s ,y s ),(x e ,y e ),then:
[0066] x s = ( 1 - x 0 ) * cos θ - ( j - y 0 ) * sin θ + x 0 y s = ( 1 - x 0 ) * sin θ + ( j - y 0 ) * cos θ + y 0 x e = ( cols - x 0 ) * cos θ - ( j - y 0 ) * sin θ + x 0 y e = ( cols - x 0 ) * sin θ + ( j - y 0 ) * cos θ + y 0
[0067] Figure 5 In order to further determine the first and last fl...
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Abstract
The invention discloses a video image rotation method. In allusion to the video image rotation methods solely using forward rotation mapping or reverse rotation mapping in the prior art, the defects are improved; and the video image rotation method comprises the steps of carrying out forward rotation mapping at first to obtain two mapping segments on a display after caching two lines of original video images, obtaining coordinates of pixel points between the two mapping segments, carrying out reverse rotation mapping on the obtained coordinates of pixel points between the two mapping segments on the display, calculating the pixel value of each coordinate after the reverse rotation mapping, and assigning the obtained pixel values to corresponding pixel point coordinates on the display for displaying. According to the method, rotation can be carried out on the video images with rotation angles between 45 DEG and -45 DEG, so that the null points generated by solely using forward rotation are effectively avoided, the cache space is saved and the real-time performance of the video displaying is improved.
Description
technical field [0001] The invention belongs to the technical field of airborne video display, and in particular relates to a video image rotation method. Background technique [0002] In the field of airborne video display, real-time video images are collected by technologies such as forward-looking infrared, millimeter-wave radar, optical amplification or night vision systems, and after a series of video processing such as video rotation, zooming, and translation, they are displayed on the monitor in the cockpit. In order to ensure the safety of aircraft operation, it is necessary to ensure that each module of video processing (including video rotation) has high real-time performance. [0003] Video rotation includes two basic operations: spatial coordinate transformation and gray level interpolation. [0004] Space coordinate transformation is divided into forward rotation mapping and reverse rotation mapping. Set the image coordinates before rotation as (x, y), around ...
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