Method for dividing quadratic Bezier curve in subtitle object vector outline by intersection points

Abstract

The invention discloses a method for dividing quadratic Bezier curve in subtitle object vector outline by intersection points, belonging to the subtitle editing-broadcasting technical field of a TV program making and broadcasting mechanism in radio industry; in the method, intersection points from S(0)to S(n-1)of all quadratic Bezier line segments and other quadratic Bezier line segments in the subtitle object vector outline are calculated; the line segment B at the S(0) point is divided into line segment B1 and line segment B1'; the ling segment B1'is divided into line segment B2 and line segment B2'at the S(1) point; by parity of reasoning, the line segment Bn-1 is divided into line segment Bn and line segment Bn'at the S(n-1) point, and finally, N+1 divided ling segments are obtained; by adopting the method in the invention, the method is beneficial to follow-up rendering of the subtitle object and the final rendering effect of the subtitle object is enhanced.

Description

technical field [0001] The invention belongs to the technical field of subtitle editing and broadcasting by TV program production and broadcasting institutions in the radio and television industry, and in particular relates to a method for dividing quadratic Bezier curves in subtitle object vector outlines according to intersection points. Background technique [0002] In the field of subtitle editing and broadcasting, subtitle objects can be divided into two parts: text and graphics. Text includes text in various languages ​​in the world, and graphics include various regular-shaped graphics, composite graphics composed of basic graphic elements, and arbitrary irregular graphics. From the perspective of computer graphics, all types of subtitle objects can be regarded as graphics composed of a series of straight lines and curves. Graphics are usually composed of geometric elements such as points, lines, surfaces, and volumes, and non-geometric attributes such as grayscale, c...

AI Technical Summary

Problems solved by technology

This problem has brought many disadvantages to the subtitle system in both implementation and application

From an implementation point of view, there will be multiple completely different rendering engines and rendering processes in a subtitle system, and if a new subtitle object is to be supported, a new rendering engine needs to be defined and implemented, resulting in subtitle system There are great limitations in the functional scalability of

From the application point of view, it brings two fatal problems: on the one hand, different types of subtitle objects have inconsistent final display effects. After different rendering engines, the final processing results may be different, which brings a lot of inconvenience to users when creating subtitles; on the other hand, in the subtitle system, the operation of subtitle objects has to be restricted. For example, some subtitle objects support geometric rotation and geometric scaling, while others do not; not support

This will lead to two problems: on the one hand, since the final processing result requires integer pixel values, rounding operations will be performed at different stages of the rendering engine algorithm, which will cause cumulative errors in calculation, resulting in the final The subtitle effect has defects in local details, such as blurred text with many strokes, sticky strokes, etc.; on the other hand, these floating-point operations are mathematical operations that take up a lot of machine instructions, which greatly reduces the work efficiency of the entire subtitle system , affecting the timeliness of subtitle production and broadcasting, especially in the production of high-definition TV subtitles, because the amount of data is 5 times that of standard definition, this is more obvious

[0008]Third, as one of the important indicators of subtitle rendering, the effect of edge anti-aliasing is not ideal, and it cannot even reach a practical level

[0011] Fourth, when a subtitle object performs gradient color rendering, it should perform radial gradient color processing according to the vector outline of the object, but in the existing subtitle In the system, the rendering process of the gradient color is to put the gradient color in a memory block, and when rendering, the method of corresponding pixel map is adopted

This makes the existing subtitle system unable to achieve the rendering effect of gradient color in the true sense

[0012]Fifth, the existing subtitle system cannot add multiple outer edges, multiple inner edges, multiple side three-dimensional edges, and multiple shadows

The superimposed subtitle display of the simple surface, edge and shadow can no longer meet the requirements of the subtitle system for TV program production

[0013]Sixth, the rendering of existing subtitle systems is not based on Bezier curve outlines, but since the fonts in the TrueType font library are all described by Bezier curves, it is It is necessary to convert the Bezier curve extracted from the font library into another form of vector. Due to the information asymmetry between different vector expressions, information loss will occur during the conversion process, which will deform the shape of the strokes, resulting in The thickness of the strokes is uneven, which affects the appearance of the font

[0014] Seventh, the existing subtitle system cannot convert text subtitle objects into graphic subtitle objects, so that character deformation, character reflection, character reversal, and curve placement cannot be realized , WordArt and other functions, which cannot meet the needs of advanced subtitle applications

Not only that, there may also be intersections between multiple closed contours contained in a subtitle object. If this situation is not handled, it will affect the final rendering effect of the subtitle object

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