Bug 274249 – Safari 17.4 does not support PNG images with 1-bit grayscale and simple transparency (tRNS chunk)

• Status: RESOLVED
• Resolution: MOVED
• Component: Images

[Stéphane Magnenat]

Created attachment 471420 [details]
A PNG valid according to pngcheck but that cannot be loaded by Safari

Safari is not able to load the attached PNG (EncodingError: Loading error), which is valid according to `pngcheck`:

```
pngcheck -v png_not_work_in_safari.png 
File: png_not_work_in_safari.png (287 bytes)
  chunk IHDR at offset 0x0000c, length 13
    1599 x 994 image, 1-bit grayscale, non-interlaced
  chunk tRNS at offset 0x00025, length 2
    gray = 0x0000
  chunk IDAT at offset 0x00033, length 216
    zlib: deflated, 32K window, superfast compression
  chunk IEND at offset 0x00117, length 0
No errors detected in png_not_work_in_safari.png (4 chunks, 99.9% compression).
```

The PNG was generated by zopflipng (https://github.com/google/zopfli/) version 1.0.3 as part of a batch optimization of a game asset database.

[Stéphane Magnenat]

Note that this image works fine with Firefox or Chrome.

[Radar WebKit Bug Importer]

<rdar://problem/128197007>

[Alexey Proskuryakov]

This image also fails to open in Preview, so this is an issue in underlying system frameworks that other browsers don't use, not in WebKit. 

Thank you for the report, Apple will continue working on this internally.