From 976fd9687e5773f3653385da7a3489ce4d58dd51 Mon Sep 17 00:00:00 2001 From: DRC Date: Tue, 13 May 2014 18:41:33 +0000 Subject: [PATCH] The x86/x86-64 SIMD extensions were originally designed to accommodate changing the value of RGB_*, but this apparently broke when RGB-to-gray colorspace conversion was accelerated. Further, the ARM NEON extensions have always assumed that JCS_RGB behaves identically to JCS_EXT_RGB. Rather than fix these issues, it makes more sense to just stop claiming that we support changing the values of RGB_*, since doing so is no longer necessary. git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1298 632fc199-4ca6-4c93-a231-07263d6284db --- jmorecfg.h | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/jmorecfg.h b/jmorecfg.h index f41eccf..155473e 100644 --- a/jmorecfg.h +++ b/jmorecfg.h @@ -298,18 +298,24 @@ typedef int boolean; /* - * Ordering of RGB data in scanlines passed to or from the application. - * If your application wants to deal with data in the order B,G,R, just - * change these macros. You can also deal with formats such as R,G,B,X - * (one extra byte per pixel) by changing RGB_PIXELSIZE. Note that changing - * the offsets will also change the order in which colormap data is organized. - * RESTRICTIONS: - * 1. The sample applications cjpeg,djpeg do NOT support modified RGB formats. - * 2. These macros only affect RGB<=>YCbCr color conversion, so they are not - * useful if you are using JPEG color spaces other than YCbCr or grayscale. - * 3. The color quantizer modules will not behave desirably if RGB_PIXELSIZE - * is not 3 (they don't understand about dummy color components!). So you - * can't use color quantization if you change that value. + * The RGB_RED, RGB_GREEN, RGB_BLUE, and RGB_PIXELSIZE macros are a vestigial + * feature of libjpeg. The idea was that, if an application developer needed + * to compress from/decompress to a BGR/BGRX/RGBX/XBGR/XRGB buffer, they could + * change these macros, rebuild libjpeg, and link their application statically + * with it. In reality, few people ever did this, because there were some + * severe restrictions involved (cjpeg and djpeg no longer worked properly, + * compressing/decompressing RGB JPEGs no longer worked properly, and the color + * quantizer wouldn't work with pixel sizes other than 3.) Further, since all + * of the O/S-supplied versions of libjpeg were built with the default values + * of RGB_RED, RGB_GREEN, RGB_BLUE, and RGB_PIXELSIZE, many applications have + * come to regard these values as immutable. + * + * The libjpeg-turbo colorspace extensions provide a much cleaner way of + * compressing from/decompressing to buffers with arbitrary component orders + * and pixel sizes. Thus, we do not support changing the values of RGB_RED, + * RGB_GREEN, RGB_BLUE, or RGB_PIXELSIZE. In addition to the restrictions + * listed above, changing these values will also break the SIMD extensions and + * the regression tests. */ #define RGB_RED 0 /* Offset of Red in an RGB scanline element */ -- 2.49.0