PNG sequence to GIF, on white
Transparent PNG pixels are painted on white during export. This page does not keep an alpha channel, and it is not a transparent-GIF maker.
Make a GIF from photosWhite is part of the export
The browser worker paints the frame canvas white, draws the photo, then quantizes those opaque pixels. GIF transparency is never requested. A logo with a soft green shadow therefore loses the shadow’s alpha and keeps a light green fringe on white.
That is a property of this exporter. Other sites that advertise a transparent result are describing their own encoder, not this one.
The same circle, two inputs
The fixture is a 180 by 180 green disc. Inside 52 pixels of the center it is opaque. From there to 70 pixels the alpha falls off. One file is that disc flattened onto white at encode time. The other is the same flattening done before encode. The GIF bytes match.
| Input | Bytes | File |
|---|---|---|
| Alpha disc, flattened at encode time | 4,385 | png-transparent-composited.gif |
| Same disc already on white | 4,385 | png-prebacked.gif |
How to prepare PNGs
- Decide the background first. Paint it into the PNG if it should not be white.
- Align screenshots on the same canvas so text does not jump between frames.
- Give a text frame a longer hold by duplicating that PNG in the list, or raise Time per photo for the whole GIF.
- Check the first frame alone. Some inboxes show only that frame.
Limits
A 256-color GIF still cannot store every antialiased edge. The quality page separates that banding from a photo that was already soft. This page only settles the background color.
Questions
Will the checkerboard in my PNG stay transparent?
No. The encoder fills the canvas with white before it draws each frame. Transparent pixels become white. Soft edges become a pale mix of the pixel color and white.
Should I add the background before export?
Yes, if you want any color other than white. A PNG that is already on white matches a transparent PNG of the same visible pixels. In the fixture, both GIFs are 4,385 bytes.
Do screenshots with text survive?
They survive as opaque pixels on white. Thin gray text on transparency will look lighter after it is mixed with white. Put the text on the background color you actually want, then export.
Can I ask for a transparent GIF?
Not with this editor. Adding that would be a different product. The files linked here are the current behavior.
Related
JPEG sequencesPalette banding and blurProduct photo sequence
Sources
- Alpha flattened in the fixture. Same byte length as the pre-backed file after both were composited on white.