From 5f7bec693d3d383061586d6f29f4fea2648399a7 Mon Sep 17 00:00:00 2001 From: Nigel Tao Date: Wed, 8 Aug 2012 09:57:09 +1000 Subject: [PATCH] image/jpeg: send a correct Start Of Scan (SOS) header. Section B.2.3 of http://www.w3.org/Graphics/JPEG/itu-t81.pdf discusses the End of spectral selection (Se) byte. Apparently many JPEG decoders ignore the Se byte (or let it through with a warning), but some configurations reject them. For example, http://download.blender.org/source/chest/blender_2.03_tree/jpeg/jcmaster.c has these lines: if (Ss != 0 || Se != DCTSIZE2-1 || Ah != 0 || Al != 0) ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); Fixes #3916. R=r CC=golang-dev https://golang.org/cl/6459052 --- src/pkg/image/jpeg/writer.go | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/pkg/image/jpeg/writer.go b/src/pkg/image/jpeg/writer.go index 3322c09fe71..d539b1da908 100644 --- a/src/pkg/image/jpeg/writer.go +++ b/src/pkg/image/jpeg/writer.go @@ -433,10 +433,12 @@ func scale(dst *block, src *[4]block) { // - component 1 uses DC table 0 and AC table 0 "\x01\x00", // - component 2 uses DC table 1 and AC table 1 "\x02\x11", // - component 3 uses DC table 1 and AC table 1 "\x03\x11", -// - padding "\x00\x00\x00". +// - the bytes "\x00\x3f\x00". Section B.2.3 of the spec says that for +// sequential DCTs, those bytes (8-bit Ss, 8-bit Se, 4-bit Ah, 4-bit Al) +// should be 0x00, 0x3f, 0x00<<4 | 0x00. var sosHeader = []byte{ 0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02, - 0x11, 0x03, 0x11, 0x00, 0x00, 0x00, + 0x11, 0x03, 0x11, 0x00, 0x3f, 0x00, } // writeSOS writes the StartOfScan marker.