GIF 拆分成帧

Inside a GIF, most frames are not whole pictures. An optimised file stores only the rectangle that changed, marks unchanged pixels as transparent, and tells the viewer whether to keep, clear or restore that area before the next frame. Extracting those raw patches gives you a pile of strips and holes.

The splitter replays the animation the way a browser does: it draws each patch on top of the previous result, applies the disposal method of the frame before it (keep, clear to transparent, or restore what was there), and saves the result. So frame 17 is the picture you saw at frame 17, background included. Areas that are transparent in the animation stay transparent in the PNG.

Each tile lists the frame’s delay in milliseconds. GIF stores delays in hundredths of a second; a delay of 0 or 10 ms is shown as 100 ms because that is how Chrome, Firefox and Safari actually play it. Adding up the delays gives the loop length, which also appears in the details panel next to the dimensions and frame count.

Files are named after the GIF with a zero-padded frame number, such as party-frame-001.png to party-frame-030.png, so they sort in order in any file manager and import in sequence into video editors or sprite tools. The ZIP is called party-frames.zip.

PNG is lossless, so the frames keep every pixel of the GIF exactly, but a folder of full frames is usually larger than the GIF itself, which stores only the changes. Our 320×200 test GIF with 30 frames is 429,740 bytes; its 30 PNG frames came to a 449,881-byte ZIP in Chrome.

The splitter opens one GIF of up to 50 MB at a time and handles up to 1,000 frames. Frames are converted one after another and appear in the grid as they are ready; for a long animation the first tiles show up while the rest are still being written.

Picking a clean still for a thumbnail or a slide, where the first frame is often blank or mid-fade. Pulling a sprite sheet apart to edit single poses. Checking a bug report recording frame by frame to see exactly when a glitch appears. Feeding frames into an editor to retime, crop or caption them, then building a new animation.