From 463b81de2b252691d75417643597c42684bf830d Mon Sep 17 00:00:00 2001 From: wm4 Date: Sat, 22 Jul 2017 23:05:14 +0200 Subject: imgutils: add function to clear an image to black Black isn't always just memset(ptr, 0, size). Limited YUV in particular requires relatively non-obvious values, and filling a frame with repeating 0 bytes is disallowed in some contexts. With component sizes larger than 8 or packed YUV, this can become relatively complicated. So having a generic function for this seems helpful. In order to handle the complex cases in a generic way without destroying performance, this code attempts to compute a black pixel, and then uses that value to clear the image data quickly by using a function like memset. Common cases like yuv410p10 or rgba can't be handled with a simple memset, so there is some code to fill memory with 2/4/8 byte patterns. For the remaining cases, a generic slow fallback is used. Signed-off-by: Anton Khirnov Merged from Libav commit 45df7adc1d9b7. --- libavutil/imgutils.h | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'libavutil/imgutils.h') diff --git a/libavutil/imgutils.h b/libavutil/imgutils.h index ea083b10f1..2ab90ac033 100644 --- a/libavutil/imgutils.h +++ b/libavutil/imgutils.h @@ -238,6 +238,33 @@ int av_image_check_size2(unsigned int w, unsigned int h, int64_t max_pixels, enu */ int av_image_check_sar(unsigned int w, unsigned int h, AVRational sar); +/** + * Overwrite the image data with black. This is suitable for filling a + * sub-rectangle of an image, meaning the padding between the right most pixel + * and the left most pixel on the next line will not be overwritten. For some + * formats, the image size might be rounded up due to inherent alignment. + * + * If the pixel format has alpha, the alpha is cleared to opaque. + * + * This can return an error if the pixel format is not supported. Normally, all + * non-hwaccel pixel formats should be supported. + * + * Passing NULL for dst_data is allowed. Then the function returns whether the + * operation would have succeeded. (It can return an error if the pix_fmt is + * not supported.) + * + * @param dst_data data pointers to destination image + * @param dst_linesize linesizes for the destination image + * @param pix_fmt the pixel format of the image + * @param range the color range of the image (important for colorspaces such as YUV) + * @param width the width of the image in pixels + * @param height the height of the image in pixels + * @return 0 if the image data was cleared, a negative AVERROR code otherwise + */ +int av_image_fill_black(uint8_t *dst_data[4], const ptrdiff_t dst_linesize[4], + enum AVPixelFormat pix_fmt, enum AVColorRange range, + int width, int height); + /** * @} */ -- cgit v1.2.3