mirror of https://github.com/nothings/stb.git
Sean Barrett
parent
de385bb6bb
commit
53ca163e85
64
stb_image.h
64
stb_image.h
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@ -39,12 +39,21 @@
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- PPM and PGM binary formats are now supported, thanks to Ken Miller.
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- x86 platforms now make use of SSE2 SIMD instructions for
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JPEG decoding, and ARM platforms use NEON SIMD. This release is
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2x faster on our test JPEGs on x86 (except progressive JPEGs,
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which see much less speedup), mostly due to the addition of SIMD.
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This work was done by Fabian "ryg" Giesen.
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JPEG decoding, and ARM platforms can use NEON SIMD if requested.
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This work was done by Fabian "ryg" Giesen. SSE2 is used by
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default, but NEON must be enabled explicitly; see docs.
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- Compilation of SIMD code can be suppressed with
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With other JPEG optimizations included in this version, we see
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2x speedup on a JPEGs on an x86 machine, and a 1.5x speedup
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on a JPEG on an ARM machine, relative to previous versions of this
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library. The same results will not obtain for all JPGs and for all
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X86/ARM machines. (Note that progressive JPEGs are significantly
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slower to decode than regular JPEGs.) This doesn't mean that this
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is the fastest JPEG decoder in the land; rather, it brings it
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closer to parity with standard libraries. If you want the fastest
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decode, look elsewhere. (See "Philosophy" section of docs below.)
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- Compilation of all SIMD code can be suppressed with
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#define STBI_NO_SIMD
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It should not be necessary to disable it unless you have issues
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compiling (e.g. using an x86 compiler which doesn't support SSE
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@ -76,7 +85,7 @@
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Please note that STBI_JPEG_OLD is a temporary feature; it will be
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removed in future versions of the library. It is only intended for
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back-compatibility use.
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near-term back-compatibility use.
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- Added STBI_MALLOC, STBI_REALLOC, and STBI_FREE macros for replacing
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the memory allocator. Unlike other STBI libraries, these macros don't
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@ -86,7 +95,7 @@
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Latest revision history:
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2.00 (2014-12-25) optimize JPEG, incl. x86 & NEON SIMD
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2.00 (2014-12-25) optimize JPEG, including x86 SSE2 & ARM NEON SIMD
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progressive JPEG
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PGM/PPM support
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STBI_MALLOC,STBI_REALLOC,STBI_FREE
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@ -136,7 +145,7 @@
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License:
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This software is in the public domain. Where that dedication is not
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recognized, you are granted a perpetual, irrevocable license to copy
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and modify this file as you see fit.
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and modify this file however you want.
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*/
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@ -199,6 +208,29 @@ License:
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//
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// ===========================================================================
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//
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// Philosophy
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//
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// stb libraries are designed with the following priorities:
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//
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// 1. easy to use
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// 2. easy to maintain
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// 3. good performance
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//
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// Sometimes I let "good performance" creep up in priority over "easy to maintain",
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// and for best performance I may provide less-easy-to-use APIs that give higher
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// performance, in addition to the easy to use ones. Nevertheless, it's important
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// to keep in mind that from the standpoint of you, a client of this library,
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// all you care about is #1 and #3, and stb libraries do not emphasize #3 above all.
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//
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// Some secondary priorities arise directly from the first two, some of which
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// make more explicit reasons why performance can't be emphasized.
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//
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// - Portable ("ease of use")
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// - Small footprint ("easy to maintain")
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// - No dependencies ("ease of use")
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//
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// ===========================================================================
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//
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// I/O callbacks
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//
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// I/O callbacks allow you to read from arbitrary sources, like packaged
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@ -213,16 +245,17 @@ License:
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//
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// SIMD support
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//
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// The JPEG decoder will try to automatically use SIMD kernels on when
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// supported by the compiler.
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// The JPEG decoder will try to automatically use SIMD kernels on x86 when
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// supported by the compiler. For ARM Neon support, you must explicitly
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// request it.
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//
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// (The old do-it-yourself SIMD API is no longer supported in the current
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// code.)
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//
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// On x86, SSE2 will automatically be used when available; if not, the
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// generic C versions are used as a fall-back. On ARM targets, the typical
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// path is to have separate builds for NEON and non-NEON devices (at least
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// this is true for iOS and Android). Therefore, the NEON support is
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// On x86, SSE2 will automatically be used when available based on a run-time
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// test; if not, the generic C versions are used as a fall-back. On ARM targets,
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// the typical path is to have separate builds for NEON and non-NEON devices
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// (at least this is true for iOS and Android). Therefore, the NEON support is
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// toggled by a build flag: define STBI_NEON to get NEON loops.
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//
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// The output of the JPEG decoder is slightly different from versions where
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@ -1722,7 +1755,6 @@ static void stbi__idct_block(stbi_uc *out, int out_stride, short data[64])
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}
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#ifdef STBI_SSE2
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// sse2 integer IDCT. not the fastest possible implementation but it
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// produces bit-identical results to the generic C version so it's
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// fully "transparent".
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@ -2966,7 +2998,9 @@ static void stbi__setup_jpeg(stbi__jpeg *j)
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#ifdef STBI_NEON
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j->idct_block_kernel = stbi__idct_neon;
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#ifndef STBI_JPEG_OLD
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j->YCbCr_to_RGB_kernel = stbi__YCbCr_to_RGB_simd;
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#endif
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j->resample_row_hv_2_kernel = stbi__resample_row_hv_2_simd;
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#endif
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}
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