将填充颜色添加到 none 或 alpha 0，在使用 ffmpeg-python 时返回渲染视频中的绿色背景

Question

I am using ffmpeg-python (the wrapper for ffmpeg written in python) Below is the sample code mentioned.

                     inp.filter_multi_output('split')[k]
                        .filter_('rotate', a=rotation, fillcolor='#00FF0000',  ow=f"rotw({rotation})", oh=f"roth({rotation})")
                        .filter_('scale', width=(i['width'] * Factors().factors['w_factor']), height=(i['height'] * Factors().factors['h_factor'])).filter('setsar', '1/1')
                        .setpts(f"PTS-STARTPTS+{i['showtime']}/TB")

Answer 1

Transparent background in rotate filter

Use fillcolor=none . From the rotate filter documentation :

fillcolor , c
Set the color used to fill the output area not covered by the rotated image. If the special value none is selected then no background is printed. Default value is black .

Green output

If the background is green then either your output does not support alpha and/or the input had no alpha channel before giving it to the rotate filter. If the latter is the case use the format filter to add an alpha channel before the rotate filter. Simplified ffmpeg example:

ffmpeg -i input.jpg -vf "format=rgba,rotate=PI/6:fillcolor=none" output.png

See ffmpeg -pix_fmts for a list of pixel formats accepted by the format filter. Choose one with a in the name, such as rgba or yuva420p .

Answer 2

                   inp.filter_multi_output('split')[k]
                       .filter_('scale', width=(i['width'] * Factors().factors['w_factor']), height=(i['height'] * Factors().factors['h_factor'])).filter('setsar', '1/1')
                        .filter_('rotate', a=rotation, fillcolor='#00FF0000',  ow=f"rotw({rotation})", oh=f"roth({rotation})")
                        .setpts(f"PTS-STARTPTS+{i['showtime']}/TB")

Just Apply the scaling before the rotation and the problem will be resolved.