Both decoders treated every 3-component image as YCbCr, so RGB JPEGs
(as written by cjpeg -rgb, and by some Adobe software) came out with
wrong colours.
Decide the colour space as libjpeg does: a JFIF marker means YCbCr;
otherwise the transform flag of an Adobe APP14 marker decides (0 is
RGB); otherwise component IDs 'R', 'G', 'B' mean RGB.
Core loader: on colour targets R, G and B are stored in place in the
row buffer and the YUV conversion is skipped. Greyscale builds now
also decode G and B for RGB and combine them into luma per block,
which needs every component to be one block per MCU; other RGB
layouts are rejected there.
Plugin: RGB needs one block per MCU for every component, otherwise it
is rejected (colour targets fall back to jpegp). Colour builds convert
the R, G and B planes to YCbCr in place after decoding, so display and
greyscale view modes are unchanged; greyscale builds combine R, G and
B into luma per block as the core does.
Code size on the e200: core loader +351 bytes, plugin decoder +603
bytes.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Change-Id: Ib24a0b7690ca4c00b3ac01b2f511309efeac5975
Both JPEG decoders ignored the Tq selector in the frame header and
always dequantized luma with table 0 and chroma with table 1. Files
with a single shared table multiplied chroma by an empty table, and
files with separate Cb and Cr tables used the wrong one for Cr.
imageviewer/jpeg: build one dequantization table per component (3
instead of 2, +256 bytes) from the table it selects. tab_membership is
no longer used and is removed.
Core loader: the raw tables are pre-scaled in place for the IDCT, and
luma and chroma can use different IDCT scales. fix_quant_tables() now
maps each component to a table slot, copying a table that luma and
chroma share at different scales to a slot no component uses (there are
4 slots and at most 3 components, so one is always free), and rewrites
quanttable_select to that slot. No extra memory.
Selectors above 3 are rejected.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Change-Id: If04c61fb0fef95da11d98d9918ea7225d8a440b0
Both JPEG decoders ignored the DC/AC table selectors in the SOS header
and always decoded luma with tables 0 and chroma with tables 1, the
layout libjpeg writes by default. Files where all components share
table 0, or where the slots are assigned differently, decoded to noise.
Look up each component's tables from its selectors instead. Baseline
JPEG only allows tables 0 and 1, which both decoders already hold, so
this needs no extra memory; selectors above 1 are rejected. In the core
loader tab_membership is no longer used and is removed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Change-Id: Ie1ec407ddecf1256fef410b1256b97af412fb194
* Created new directory, imageviewer/ and moved both jpeg/ and png/ under it.
- this still doesn't merge the two plugins. i.e. both jpeg.rock and png.rock will be made for color targets.
- I'm thinking to merge the two plugins to single image viewer later.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24272 a1c6a512-1295-4272-9138-f99709370657
2010-01-18 12:46:19 +00:00
Renamed from apps/plugins/jpeg/jpeg_decoder.h (Browse further)
