The Web app could only render text. Now it decodes and displays images, so a
picture on the web actually shows up.
- lib/inflate.c DEFLATE / zlib decompressor (RFC 1950/1951): the algorithm
every PNG needs. Canonical Huffman, all three block types,
decodes into a caller buffer -- no allocation, integer only.
- lib/image.c PNG decoder (8-bit RGB/RGBA/grayscale/gray+alpha, and
1/2/4/8-bit grayscale & palette, non-interlaced; tRNS
transparency) plus BMP (24/32-bit). Parses chunks,
inflates IDAT, undoes the five scanline filters, and expands
to a flat 0xAARRGGBB buffer ready for gui_gfx_blit. A pixel
cap guards the heap.
- Web app: if a response body sniffs as an image it is decoded once and drawn
instead of text -- scaled to fit the panel width, vertically scrollable,
alpha-composited over the background. The per-fetch cap grew to 128 KB so
real images and longer pages fit.
Both decoders were verified on the host against generated references before
going in the kernel: inflate round-trips six zlib/raw streams (empty, back-
references, dynamic Huffman, stored blocks, 20 KB random, mixed); the image
decoder reproduces PIL-made PNGs of every supported colour type -- grayscale,
RGB, RGBA, 4-bit palette, gray+alpha -- and a BMP, with exact pixel matches.
In QEMU the Web app fetched a 360x240 PNG over HTTP and rendered it perfectly:
gradient, an antialiased red circle, a green box, a yellow diagonal, shown as
"image 360x240". Builds clean on x86_64, aarch64 and armv8i.
Still image-by-URL, not inline <img> within a page (that needs sub-resource
fetching and layout); and no JPEG/GIF (different codecs). PNG and BMP cover a
large share of the web's images.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Fh5z6V7nGPbHvqVG5p4CXX
