Empty webp versions

I’ve noticed this issue recently on PNG images with transparency that I have shrunk using TinyPNG.com, which seems to convert images colour mode from TrueColorAlpha to PaletteAlpha.

?$ identify -verbose?original.png | grep "Type"
Type: TrueColorAlpha

?$ identify -verbose?minified.png | grep "Type"
Type: PaletteAlpha

Regenerating the two images

$ sudo -u apacheuser wp media regenerate 32694 32751 --url=example.com
Found 2 images to regenerate.
1/2 Regenerated thumbnails for "minified" (ID 32751).
Warning: imagewebp(): Palette image not supported by webp in /var/www/example.com/wp-includes/class-wp-image-editor.php on line 572
2/2 Regenerated thumbnails for "minified" (ID 32694).
Success: Regenerated 2 of 2 images.

The result: original works but minified gives a zero size file.

$ ls -l wp-content/uploads/2025/02/
-rw-r--r-- 1 apacheuser apachegroup 69166 Feb 11 11:19 wp-content/uploads/2025/02/original.png
-rw-r--r-- 1 apacheuser apachegroup 20064 Feb 11 11:20 wp-content/uploads/2025/02/original-png.webp
-rw-r--r-- 1 apacheuser apachegroup 48600 Feb 11 07:56 wp-content/uploads/2025/02/minified.png
-rw-r--r-- 1 apacheuser apachegroup 0 Feb 11 11:20 wp-content/uploads/2025/02/minified-png.webp

• This reply was modified 2 weeks, 6 days ago by Jeremy Varnham. Reason: formatting

-rw-r--r-- 1 someuser someuser 13412 2025-02-07 08:18 image-name-1024x576.webp
-rw-r--r-- 1 someuser someuser   858 2025-02-07 08:18 image-name-150x150.webp
-rw-r--r-- 1 someuser someuser 25160 2025-02-07 08:18 image-name-1536x864.webp
-rw-r--r-- 1 someuser someuser  2052 2025-02-07 08:18 image-name-300x169.webp
-rw-r--r-- 1 someuser someuser  9086 2025-02-07 08:18 image-name-768x432.webp
-rw-r--r-- 1 someuser someuser 33812 2025-02-07 08:18 image-name.png
-rw-r--r-- 1 someuser someuser     0 2025-02-07 08:18 image-name-png.webp

• This reply was modified 2 weeks, 6 days ago by Benedikt Ledl.

Thanks for the tip @jvarn13

I now re-exported the problematic images in sRGB format and it is working again.

Do you know the image-name.png colour type?

identify -verbose image-name.png | grep "Type"

If it is PaletteAlpha or Palette, this might be the same problem (webp not supporting palette colour types causing the conversion to fail).

PNG color types:

Grayscale Only shades of gray, no color, no transparency.
TrueColor Full RGB colors, no transparency.
Indexed (Palette) Uses a limited palette of colors (indexed color mode).
GrayscaleAlpha Grayscale with transparency.
TrueColorAlpha Full RGB colors with transparency (RGBA).
PaletteAlpha Indexed (palette-based) colors with transparency.

Great! You posted your second reply as I was still writing ??

Even tho the problem was solved for me, I’ll still document this here if anyone needs it in the future.

The type of these broken images is “Palette”.

identify -verbose problem-image.png | grep "Type"
  Type: Palette

• This reply was modified 2 weeks, 6 days ago by Benedikt Ledl.