Guillem Hermida 359a3f2f09 M11: Optimize keeps a JPEG's colour transform (#1201) ...

Optimize decoded DCT images with the generic JPEG decoder, which converts
three components from YCbCr to RGB whenever the JPEG itself doesn't say
otherwise, and then dropped /DecodeParms. An RGB JPEG stored untransformed
(/ColorTransform 0 and no Adobe marker) therefore came out in other colours
when recompressed, resampled or merged from strips.

The samples are now read with the colour transform ISO 32000-2 §7.4.8
gives them: an Adobe APP14 marker's flag, else /ColorTransform (default 1).
Untransformed samples are taken as stored, and the result is written as a
plain YCbCr JPEG (or Flate), which needs no /DecodeParms. When the marker
and /ColorTransform disagree, a value is out of range, the parameters are
not paired with the filter as §7.4 pairs them, or the decoder reads the
components otherwise (named R, G and B), the image is left as it is.

The tests draw each image with PdfCraft's renderer before and after
Optimize: RGB JPEGs with and without an Adobe marker under each
/ColorTransform, CMYK JPEGs (still left alone) and JPEG strips merged into
one picture.

Part of #1201.

2026-10-16 17:28:19 +02:00

..

jpeg_color_transform.rs

M11: Optimize keeps a JPEG's colour transform (#1201)

2026-10-16 17:28:19 +02:00

optimize.rs

fix: Space Audit lines up its columns and counts form fonts as fonts (#2118)

2026-10-15 02:45:58 -04:00