How can I use FFmpeg to overlay an image onto a GIF and produce a new GIF that precisely matches the duration, frame count, and frame rate of the original GIF, regardless of its specific attributes? I have an existing FFmpeg command that creates an output GIF with a fixed duration of 3 seconds. However, I need a more dynamic solution that automatically adjusts to the length of any input GIF. This means the output GIF should have the same number of frames and frames per second (FPS) as the input GIF, ensuring a consistent playback speed and duration.
The goal is to create a command that can adapt to various input GIFs, each potentially having different lengths and frame rates, without manually adjusting the command for each file. How can I achieve this level of automation in my FFmpeg command?
You can accomplish this with the FFmpeg
-filter_complex option. Here’s a basic command structure you can follow:
ffmpeg -i input.gif -i overlay.png -filter_complex "  overlay" -f gif output.gif
This command takes your input GIF (input.gif) and the image you wish to overlay (overlay.png). It then overlays the image onto the GIF using
-filter_complex. The output is a GIF file, and this command should automatically keep the original GIF’s duration and frame rate.
That’s useful. However, I’m concerned about preserving the quality of the original GIF. What should I add to the command to ensure this?
Good point. To maintain the quality, you can enhance the command like this:
ffmpeg -i input.gif -i overlay.png -filter_complex "  overlay" -lavfi palettegen=max_colors=256:stats_mode=diff palette.png; ffmpeg -i input.gif -i overlay.png -i palette.png -filter_complex "  overlay, paletteuse=dither=bayer:bayer_scale=5" -f gif output.gif
This enhanced command first generates a color palette from the original GIF, which helps in preserving the color range and quality. Then, it applies this palette to the final GIF, aiming to keep the quality as close to the original as possible.
That’s quite comprehensive. But what if my overlay image is a different size than the GIF? How does the command handle resizing or repositioning?
If the overlay image size differs from your GIF, FFmpeg will place it based on the frame’s top-left corner by default. For different positioning or resizing, you can modify the overlay filter like so:
This modification centers the overlay image on the GIF. You can alter the x and y values to position the image as you see fit. For resizing, the scale filter can be used before overlaying. FFmpeg offers great flexibility, allowing you to tailor these commands to your specific requirements.