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stb_image.c
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/* stbi-1.33 - public domain JPEG/PNG reader - http://nothings.org/stb_image.c
when you control the images you're loading
no warranty implied; use at your own risk
QUICK NOTES:
Primarily of interest to game developers and other people who can
avoid problematic images and only need the trivial interface
JPEG baseline (no JPEG progressive)
PNG 8-bit only
TGA (not sure what subset, if a subset)
BMP non-1bpp, non-RLE
PSD (composited view only, no extra channels)
GIF (*comp always reports as 4-channel)
HDR (radiance rgbE format)
PIC (Softimage PIC)
- decode from memory or through FILE (define STBI_NO_STDIO to remove code)
- decode from arbitrary I/O callbacks
- overridable dequantizing-IDCT, YCbCr-to-RGB conversion (define STBI_SIMD)
Latest revisions:
1.33 (2011-07-14) minor fixes suggested by Dave Moore
1.32 (2011-07-13) info support for all filetypes (SpartanJ)
1.31 (2011-06-19) a few more leak fixes, bug in PNG handling (SpartanJ)
1.30 (2011-06-11) added ability to load files via io callbacks (Ben Wenger)
1.29 (2010-08-16) various warning fixes from Aurelien Pocheville
1.28 (2010-08-01) fix bug in GIF palette transparency (SpartanJ)
1.27 (2010-08-01) cast-to-uint8 to fix warnings (Laurent Gomila)
allow trailing 0s at end of image data (Laurent Gomila)
1.26 (2010-07-24) fix bug in file buffering for PNG reported by SpartanJ
See end of file for full revision history.
TODO:
stbi_info support for BMP,PSD,HDR,PIC
============================ Contributors =========================
Image formats Optimizations & bugfixes
Sean Barrett (jpeg, png, bmp) Fabian "ryg" Giesen
Nicolas Schulz (hdr, psd)
Jonathan Dummer (tga) Bug fixes & warning fixes
Jean-Marc Lienher (gif) Marc LeBlanc
Tom Seddon (pic) Christpher Lloyd
Thatcher Ulrich (psd) Dave Moore
Won Chun
the Horde3D community
Extensions, features Janez Zemva
Jetro Lauha (stbi_info) Jonathan Blow
James "moose2000" Brown (iPhone PNG) Laurent Gomila
Ben "Disch" Wenger (io callbacks) Aruelien Pocheville
Martin "SpartanJ" Golini Ryamond Barbiero
David Woo
If your name should be here but isn't, let Sean know.
*/
#ifndef STBI_INCLUDE_STB_IMAGE_H
#define STBI_INCLUDE_STB_IMAGE_H
// To get a header file for this, either cut and paste the header,
// or create stb_image.h, #define STBI_HEADER_FILE_ONLY, and
// then include stb_image.c from it.
//// begin header file ////////////////////////////////////////////////////
//
// Limitations:
// - no jpeg progressive support
// - non-HDR formats support 8-bit samples only (jpeg, png)
// - no delayed line count (jpeg) -- IJG doesn't support either
// - no 1-bit BMP
// - GIF always returns *comp=4
//
// Basic usage (see HDR discussion below):
// int x,y,n;
// unsigned char *data = stbi_load(filename, &x, &y, &n, 0);
// // ... process data if not NULL ...
// // ... x = width, y = height, n = # 8-bit components per pixel ...
// // ... replace '0' with '1'..'4' to force that many components per pixel
// // ... but 'n' will always be the number that it would have been if you said 0
// stbi_image_free(data)
//
// Standard parameters:
// int *x -- outputs image width in pixels
// int *y -- outputs image height in pixels
// int *comp -- outputs # of image components in image file
// int req_comp -- if non-zero, # of image components requested in result
//
// The return value from an image loader is an 'unsigned char *' which points
// to the pixel data. The pixel data consists of *y scanlines of *x pixels,
// with each pixel consisting of N interleaved 8-bit components; the first
// pixel pointed to is top-left-most in the image. There is no padding between
// image scanlines or between pixels, regardless of format. The number of
// components N is 'req_comp' if req_comp is non-zero, or *comp otherwise.
// If req_comp is non-zero, *comp has the number of components that _would_
// have been output otherwise. E.g. if you set req_comp to 4, you will always
// get RGBA output, but you can check *comp to easily see if it's opaque.
//
// An output image with N components has the following components interleaved
// in this order in each pixel:
//
// N=#comp components
// 1 grey
// 2 grey, alpha
// 3 red, green, blue
// 4 red, green, blue, alpha
//
// If image loading fails for any reason, the return value will be NULL,
// and *x, *y, *comp will be unchanged. The function stbi_failure_reason()
// can be queried for an extremely brief, end-user unfriendly explanation
// of why the load failed. Define STBI_NO_FAILURE_STRINGS to avoid
// compiling these strings at all, and STBI_FAILURE_USERMSG to get slightly
// more user-friendly ones.
//
// Paletted PNG, BMP, GIF, and PIC images are automatically depalettized.
//
// ===========================================================================
//
// iPhone PNG support:
//
// By default we convert iphone-formatted PNGs back to RGB; nominally they
// would silently load as BGR, except the existing code should have just
// failed on such iPhone PNGs. But you can disable this conversion by
// by calling stbi_convert_iphone_png_to_rgb(0), in which case
// you will always just get the native iphone "format" through.
//
// Call stbi_set_unpremultiply_on_load(1) as well to force a divide per
// pixel to remove any premultiplied alpha *only* if the image file explicitly
// says there's premultiplied data (currently only happens in iPhone images,
// and only if iPhone convert-to-rgb processing is on).
//
// ===========================================================================
//
// HDR image support (disable by defining STBI_NO_HDR)
//
// stb_image now supports loading HDR images in general, and currently
// the Radiance .HDR file format, although the support is provided
// generically. You can still load any file through the existing interface;
// if you attempt to load an HDR file, it will be automatically remapped to
// LDR, assuming gamma 2.2 and an arbitrary scale factor defaulting to 1;
// both of these constants can be reconfigured through this interface:
//
// stbi_hdr_to_ldr_gamma(2.2f);
// stbi_hdr_to_ldr_scale(1.0f);
//
// (note, do not use _inverse_ constants; stbi_image will invert them
// appropriately).
//
// Additionally, there is a new, parallel interface for loading files as
// (linear) floats to preserve the full dynamic range:
//
// float *data = stbi_loadf(filename, &x, &y, &n, 0);
//
// If you load LDR images through this interface, those images will
// be promoted to floating point values, run through the inverse of
// constants corresponding to the above:
//
// stbi_ldr_to_hdr_scale(1.0f);
// stbi_ldr_to_hdr_gamma(2.2f);
//
// Finally, given a filename (or an open file or memory block--see header
// file for details) containing image data, you can query for the "most
// appropriate" interface to use (that is, whether the image is HDR or
// not), using:
//
// stbi_is_hdr(char *filename);
//
// ===========================================================================
//
// I/O callbacks
//
// I/O callbacks allow you to read from arbitrary sources, like packaged
// files or some other source. Data read from callbacks are processed
// through a small internal buffer (currently 128 bytes) to try to reduce
// overhead.
//
// The three functions you must define are "read" (reads some bytes of data),
// "skip" (skips some bytes of data), "eof" (reports if the stream is at the end).
#ifndef STBI_NO_STDIO
#if defined(_MSC_VER) && _MSC_VER >= 0x1400
#define _CRT_SECURE_NO_WARNINGS // suppress bogus warnings about fopen()
#endif
#include <stdio.h>
#endif
#define STBI_VERSION 1
enum
{
STBI_default = 0, // only used for req_comp
STBI_grey = 1,
STBI_grey_alpha = 2,
STBI_rgb = 3,
STBI_rgb_alpha = 4
};
typedef unsigned char stbi_uc;
#ifdef __cplusplus
extern "C" {
#endif
//////////////////////////////////////////////////////////////////////////////
//
// PRIMARY API - works on images of any type
//
//
// load image by filename, open file, or memory buffer
//
extern stbi_uc *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp);
#ifndef STBI_NO_STDIO
extern stbi_uc *stbi_load (char const *filename, int *x, int *y, int *comp, int req_comp);
extern stbi_uc *stbi_load_from_file (FILE *f, int *x, int *y, int *comp, int req_comp);
// for stbi_load_from_file, file pointer is left pointing immediately after image
#endif
typedef struct
{
int (*read) (void *user,char *data,int size); // fill 'data' with 'size' bytes. return number of bytes actually read
void (*skip) (void *user,unsigned n); // skip the next 'n' bytes
int (*eof) (void *user); // returns nonzero if we are at end of file/data
} stbi_io_callbacks;
extern stbi_uc *stbi_load_from_callbacks (stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp);
#ifndef STBI_NO_HDR
extern float *stbi_loadf_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp);
#ifndef STBI_NO_STDIO
extern float *stbi_loadf (char const *filename, int *x, int *y, int *comp, int req_comp);
extern float *stbi_loadf_from_file (FILE *f, int *x, int *y, int *comp, int req_comp);
#endif
extern float *stbi_loadf_from_callbacks (stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp);
extern void stbi_hdr_to_ldr_gamma(float gamma);
extern void stbi_hdr_to_ldr_scale(float scale);
extern void stbi_ldr_to_hdr_gamma(float gamma);
extern void stbi_ldr_to_hdr_scale(float scale);
#endif // STBI_NO_HDR
// stbi_is_hdr is always defined
extern int stbi_is_hdr_from_callbacks(stbi_io_callbacks const *clbk, void *user);
extern int stbi_is_hdr_from_memory(stbi_uc const *buffer, int len);
#ifndef STBI_NO_STDIO
extern int stbi_is_hdr (char const *filename);
extern int stbi_is_hdr_from_file(FILE *f);
#endif // STBI_NO_STDIO
// get a VERY brief reason for failure
// NOT THREADSAFE
extern const char *stbi_failure_reason (void);
// free the loaded image -- this is just free()
extern void stbi_image_free (void *retval_from_stbi_load);
// get image dimensions & components without fully decoding
extern int stbi_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);
extern int stbi_info_from_callbacks(stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp);
#ifndef STBI_NO_STDIO
extern int stbi_info (char const *filename, int *x, int *y, int *comp);
extern int stbi_info_from_file (FILE *f, int *x, int *y, int *comp);
#endif
// for image formats that explicitly notate that they have premultiplied alpha,
// we just return the colors as stored in the file. set this flag to force
// unpremultiplication. results are undefined if the unpremultiply overflow.
extern void stbi_set_unpremultiply_on_load(int flag_true_if_should_unpremultiply);
// indicate whether we should process iphone images back to canonical format,
// or just pass them through "as-is"
extern void stbi_convert_iphone_png_to_rgb(int flag_true_if_should_convert);
// ZLIB client - used by PNG, available for other purposes
extern char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen);
extern char *stbi_zlib_decode_malloc(const char *buffer, int len, int *outlen);
extern int stbi_zlib_decode_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);
extern char *stbi_zlib_decode_noheader_malloc(const char *buffer, int len, int *outlen);
extern int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen);
// define faster low-level operations (typically SIMD support)
#ifdef STBI_SIMD
typedef void (*stbi_idct_8x8)(stbi_uc *out, int out_stride, short data[64], unsigned short *dequantize);
// compute an integer IDCT on "input"
// input[x] = data[x] * dequantize[x]
// write results to 'out': 64 samples, each run of 8 spaced by 'out_stride'
// CLAMP results to 0..255
typedef void (*stbi_YCbCr_to_RGB_run)(stbi_uc *output, stbi_uc const *y, stbi_uc const *cb, stbi_uc const *cr, int count, int step);
// compute a conversion from YCbCr to RGB
// 'count' pixels
// write pixels to 'output'; each pixel is 'step' bytes (either 3 or 4; if 4, write '255' as 4th), order R,G,B
// y: Y input channel
// cb: Cb input channel; scale/biased to be 0..255
// cr: Cr input channel; scale/biased to be 0..255
extern void stbi_install_idct(stbi_idct_8x8 func);
extern void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func);
#endif // STBI_SIMD
#ifdef __cplusplus
}
#endif
//
//
//// end header file /////////////////////////////////////////////////////
#endif // STBI_INCLUDE_STB_IMAGE_H
#ifndef STBI_HEADER_FILE_ONLY
#ifndef STBI_NO_HDR
#include <math.h> // ldexp
#include <string.h> // strcmp, strtok
#endif
#ifndef STBI_NO_STDIO
#include <stdio.h>
#endif
#include <stdlib.h>
#include <memory.h>
#include <assert.h>
#include <stdarg.h>
#ifndef _MSC_VER
#ifdef __cplusplus
#define stbi_inline inline
#else
#define stbi_inline
#endif
#else
#define stbi_inline __forceinline
#endif
// implementation:
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef signed short int16;
typedef unsigned int uint32;
typedef signed int int32;
typedef unsigned int uint;
// should produce compiler error if size is wrong
typedef unsigned char validate_uint32[sizeof(uint32)==4 ? 1 : -1];
#if defined(STBI_NO_STDIO) && !defined(STBI_NO_WRITE)
#define STBI_NO_WRITE
#endif
#define STBI_NOTUSED(v) (void)sizeof(v)
#ifdef _MSC_VER
#define STBI_HAS_LROTL
#endif
#ifdef STBI_HAS_LROTL
#define stbi_lrot(x,y) _lrotl(x,y)
#else
#define stbi_lrot(x,y) (((x) << (y)) | ((x) >> (32 - (y))))
#endif
///////////////////////////////////////////////
//
// stbi struct and start_xxx functions
// stbi structure is our basic context used by all images, so it
// contains all the IO context, plus some basic image information
typedef struct
{
uint32 img_x, img_y;
int img_n, img_out_n;
stbi_io_callbacks io;
void *io_user_data;
int read_from_callbacks;
int buflen;
uint8 buffer_start[128];
uint8 *img_buffer, *img_buffer_end;
uint8 *img_buffer_original;
} stbi;
static void refill_buffer(stbi *s);
// initialize a memory-decode context
static void start_mem(stbi *s, uint8 const *buffer, int len)
{
s->io.read = NULL;
s->read_from_callbacks = 0;
s->img_buffer = s->img_buffer_original = (uint8 *) buffer;
s->img_buffer_end = (uint8 *) buffer+len;
}
// initialize a callback-based context
static void start_callbacks(stbi *s, stbi_io_callbacks *c, void *user)
{
s->io = *c;
s->io_user_data = user;
s->buflen = sizeof(s->buffer_start);
s->read_from_callbacks = 1;
s->img_buffer_original = s->buffer_start;
refill_buffer(s);
}
#ifndef STBI_NO_STDIO
static int stdio_read(void *user, char *data, int size)
{
return (int) fread(data,1,size,(FILE*) user);
}
static void stdio_skip(void *user, unsigned n)
{
fseek((FILE*) user, n, SEEK_CUR);
}
static int stdio_eof(void *user)
{
return feof((FILE*) user);
}
static stbi_io_callbacks stbi_stdio_callbacks =
{
stdio_read,
stdio_skip,
stdio_eof,
};
static void start_file(stbi *s, FILE *f)
{
start_callbacks(s, &stbi_stdio_callbacks, (void *) f);
}
//static void stop_file(stbi *s) { }
#endif // !STBI_NO_STDIO
static void stbi_rewind(stbi *s)
{
// conceptually rewind SHOULD rewind to the beginning of the stream,
// but we just rewind to the beginning of the initial buffer, because
// we only use it after doing 'test', which only ever looks at at most 92 bytes
s->img_buffer = s->img_buffer_original;
}
static int stbi_jpeg_test(stbi *s);
static stbi_uc *stbi_jpeg_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_jpeg_info(stbi *s, int *x, int *y, int *comp);
static int stbi_png_test(stbi *s);
static stbi_uc *stbi_png_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_png_info(stbi *s, int *x, int *y, int *comp);
static int stbi_bmp_test(stbi *s);
static stbi_uc *stbi_bmp_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_tga_test(stbi *s);
static stbi_uc *stbi_tga_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_tga_info(stbi *s, int *x, int *y, int *comp);
static int stbi_psd_test(stbi *s);
static stbi_uc *stbi_psd_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_hdr_test(stbi *s);
static float *stbi_hdr_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_pic_test(stbi *s);
static stbi_uc *stbi_pic_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_gif_test(stbi *s);
static stbi_uc *stbi_gif_load(stbi *s, int *x, int *y, int *comp, int req_comp);
static int stbi_gif_info(stbi *s, int *x, int *y, int *comp);
// this is not threadsafe
static const char *failure_reason;
const char *stbi_failure_reason(void)
{
return failure_reason;
}
static int e(const char *str)
{
failure_reason = str;
return 0;
}
// e - error
// epf - error returning pointer to float
// epuc - error returning pointer to unsigned char
#ifdef STBI_NO_FAILURE_STRINGS
#define e(x,y) 0
#elif defined(STBI_FAILURE_USERMSG)
#define e(x,y) e(y)
#else
#define e(x,y) e(x)
#endif
#define epf(x,y) ((float *) (e(x,y)?NULL:NULL))
#define epuc(x,y) ((unsigned char *) (e(x,y)?NULL:NULL))
void stbi_image_free(void *retval_from_stbi_load)
{
free(retval_from_stbi_load);
}
#ifndef STBI_NO_HDR
static float *ldr_to_hdr(stbi_uc *data, int x, int y, int comp);
static stbi_uc *hdr_to_ldr(float *data, int x, int y, int comp);
#endif
static unsigned char *stbi_load_main(stbi *s, int *x, int *y, int *comp, int req_comp)
{
if (stbi_jpeg_test(s)) return stbi_jpeg_load(s,x,y,comp,req_comp);
if (stbi_png_test(s)) return stbi_png_load(s,x,y,comp,req_comp);
if (stbi_bmp_test(s)) return stbi_bmp_load(s,x,y,comp,req_comp);
if (stbi_gif_test(s)) return stbi_gif_load(s,x,y,comp,req_comp);
if (stbi_psd_test(s)) return stbi_psd_load(s,x,y,comp,req_comp);
if (stbi_pic_test(s)) return stbi_pic_load(s,x,y,comp,req_comp);
#ifndef STBI_NO_HDR
if (stbi_hdr_test(s)) {
float *hdr = stbi_hdr_load(s, x,y,comp,req_comp);
return hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
}
#endif
// test tga last because it's a crappy test!
if (stbi_tga_test(s))
return stbi_tga_load(s,x,y,comp,req_comp);
return epuc("unknown image type", "Image not of any known type, or corrupt");
}
#ifndef STBI_NO_STDIO
unsigned char *stbi_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
FILE *f = fopen(filename, "rb");
unsigned char *result;
if (!f)
{
printf("Can't open file\n");
return epuc("can't fopen", "Unable to open file");
}
result = stbi_load_from_file(f,x,y,comp,req_comp);
fclose(f);
return result;
}
unsigned char *stbi_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_file(&s,f);
return stbi_load_main(&s,x,y,comp,req_comp);
}
#endif //!STBI_NO_STDIO
unsigned char *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_mem(&s,buffer,len);
return stbi_load_main(&s,x,y,comp,req_comp);
}
unsigned char *stbi_load_from_callbacks(stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_callbacks(&s, (stbi_io_callbacks *) clbk, user);
return stbi_load_main(&s,x,y,comp,req_comp);
}
#ifndef STBI_NO_HDR
float *stbi_loadf_main(stbi *s, int *x, int *y, int *comp, int req_comp)
{
unsigned char *data;
#ifndef STBI_NO_HDR
if (stbi_hdr_test(s))
return stbi_hdr_load(s,x,y,comp,req_comp);
#endif
data = stbi_load_main(s, x, y, comp, req_comp);
if (data)
return ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
return epf("unknown image type", "Image not of any known type, or corrupt");
}
float *stbi_loadf_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_mem(&s,buffer,len);
return stbi_loadf_main(&s,x,y,comp,req_comp);
}
float *stbi_loadf_from_callbacks(stbi_io_callbacks const *clbk, void *user, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_callbacks(&s, (stbi_io_callbacks *) clbk, user);
return stbi_loadf_main(&s,x,y,comp,req_comp);
}
#ifndef STBI_NO_STDIO
float *stbi_loadf(char const *filename, int *x, int *y, int *comp, int req_comp)
{
FILE *f = fopen(filename, "rb");
float *result;
if (!f) return epf("can't fopen", "Unable to open file");
result = stbi_loadf_from_file(f,x,y,comp,req_comp);
fclose(f);
return result;
}
float *stbi_loadf_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
stbi s;
start_file(&s,f);
return stbi_loadf_main(&s,x,y,comp,req_comp);
}
#endif // !STBI_NO_STDIO
#endif // !STBI_NO_HDR
// these is-hdr-or-not is defined independent of whether STBI_NO_HDR is
// defined, for API simplicity; if STBI_NO_HDR is defined, it always
// reports false!
int stbi_is_hdr_from_memory(stbi_uc const *buffer, int len)
{
#ifndef STBI_NO_HDR
stbi s;
start_mem(&s,buffer,len);
return stbi_hdr_test(&s);
#else
STBI_NOTUSED(buffer);
STBI_NOTUSED(len);
return 0;
#endif
}
#ifndef STBI_NO_STDIO
extern int stbi_is_hdr (char const *filename)
{
FILE *f = fopen(filename, "rb");
int result=0;
if (f) {
result = stbi_is_hdr_from_file(f);
fclose(f);
}
return result;
}
extern int stbi_is_hdr_from_file(FILE *f)
{
#ifndef STBI_NO_HDR
stbi s;
start_file(&s,f);
return stbi_hdr_test(&s);
#else
return 0;
#endif
}
#endif // !STBI_NO_STDIO
extern int stbi_is_hdr_from_callbacks(stbi_io_callbacks const *clbk, void *user)
{
#ifndef STBI_NO_HDR
stbi s;
start_callbacks(&s, (stbi_io_callbacks *) clbk, user);
return stbi_hdr_test(&s);
#else
return 0;
#endif
}
#ifndef STBI_NO_HDR
static float h2l_gamma_i=1.0f/2.2f, h2l_scale_i=1.0f;
static float l2h_gamma=2.2f, l2h_scale=1.0f;
void stbi_hdr_to_ldr_gamma(float gamma) { h2l_gamma_i = 1/gamma; }
void stbi_hdr_to_ldr_scale(float scale) { h2l_scale_i = 1/scale; }
void stbi_ldr_to_hdr_gamma(float gamma) { l2h_gamma = gamma; }
void stbi_ldr_to_hdr_scale(float scale) { l2h_scale = scale; }
#endif
//////////////////////////////////////////////////////////////////////////////
//
// Common code used by all image loaders
//
enum
{
SCAN_load=0,
SCAN_type,
SCAN_header
};
static void refill_buffer(stbi *s)
{
int n = (s->io.read)(s->io_user_data,(char*)s->buffer_start,s->buflen);
if (n == 0) {
// at end of file, treat same as if from memory
s->read_from_callbacks = 0;
s->img_buffer = s->img_buffer_end-1;
*s->img_buffer = 0;
} else {
s->img_buffer = s->buffer_start;
s->img_buffer_end = s->buffer_start + n;
}
}
stbi_inline static int get8(stbi *s)
{
if (s->img_buffer < s->img_buffer_end)
return *s->img_buffer++;
if (s->read_from_callbacks) {
refill_buffer(s);
return *s->img_buffer++;
}
return 0;
}
stbi_inline static int at_eof(stbi *s)
{
if (s->io.read) {
if (!(s->io.eof)(s->io_user_data)) return 0;
// if feof() is true, check if buffer = end
// special case: we've only got the special 0 character at the end
if (s->read_from_callbacks == 0) return 1;
}
return s->img_buffer >= s->img_buffer_end;
}
stbi_inline static uint8 get8u(stbi *s)
{
return (uint8) get8(s);
}
static void skip(stbi *s, int n)
{
if (s->io.read) {
int blen = s->img_buffer_end - s->img_buffer;
if (blen < n) {
s->img_buffer = s->img_buffer_end;
(s->io.skip)(s->io_user_data, n - blen);
return;
}
}
s->img_buffer += n;
}
static int getn(stbi *s, stbi_uc *buffer, int n)
{
if (s->io.read) {
int blen = s->img_buffer_end - s->img_buffer;
if (blen < n) {
int res, count;
memcpy(buffer, s->img_buffer, blen);
count = (s->io.read)(s->io_user_data, (char*) buffer + blen, n - blen);
res = (count == (n-blen));
s->img_buffer = s->img_buffer_end;
return res;
}
}
if (s->img_buffer+n <= s->img_buffer_end) {
memcpy(buffer, s->img_buffer, n);
s->img_buffer += n;
return 1;
} else
return 0;
}
static int get16(stbi *s)
{
int z = get8(s);
return (z << 8) + get8(s);
}
static uint32 get32(stbi *s)
{
uint32 z = get16(s);
return (z << 16) + get16(s);
}
static int get16le(stbi *s)
{
int z = get8(s);
return z + (get8(s) << 8);
}
static uint32 get32le(stbi *s)
{
uint32 z = get16le(s);
return z + (get16le(s) << 16);
}
//////////////////////////////////////////////////////////////////////////////
//
// generic converter from built-in img_n to req_comp
// individual types do this automatically as much as possible (e.g. jpeg
// does all cases internally since it needs to colorspace convert anyway,
// and it never has alpha, so very few cases ). png can automatically
// interleave an alpha=255 channel, but falls back to this for other cases
//
// assume data buffer is malloced, so malloc a new one and free that one
// only failure mode is malloc failing
static uint8 compute_y(int r, int g, int b)
{
return (uint8) (((r*77) + (g*150) + (29*b)) >> 8);
}
static unsigned char *convert_format(unsigned char *data, int img_n, int req_comp, uint x, uint y)
{
int i,j;
unsigned char *good;
if (req_comp == img_n) return data;
assert(req_comp >= 1 && req_comp <= 4);
good = (unsigned char *) malloc(req_comp * x * y);
if (good == NULL) {
free(data);
return epuc("outofmem", "Out of memory");
}
for (j=0; j < (int) y; ++j) {
unsigned char *src = data + j * x * img_n ;
unsigned char *dest = good + j * x * req_comp;
#define COMBO(a,b) ((a)*8+(b))
#define CASE(a,b) case COMBO(a,b): for(i=x-1; i >= 0; --i, src += a, dest += b)
// convert source image with img_n components to one with req_comp components;
// avoid switch per pixel, so use switch per scanline and massive macros
switch (COMBO(img_n, req_comp)) {
CASE(1,2) dest[0]=src[0], dest[1]=255; break;
CASE(1,3) dest[0]=dest[1]=dest[2]=src[0]; break;
CASE(1,4) dest[0]=dest[1]=dest[2]=src[0], dest[3]=255; break;
CASE(2,1) dest[0]=src[0]; break;
CASE(2,3) dest[0]=dest[1]=dest[2]=src[0]; break;
CASE(2,4) dest[0]=dest[1]=dest[2]=src[0], dest[3]=src[1]; break;
CASE(3,4) dest[0]=src[0],dest[1]=src[1],dest[2]=src[2],dest[3]=255; break;
CASE(3,1) dest[0]=compute_y(src[0],src[1],src[2]); break;
CASE(3,2) dest[0]=compute_y(src[0],src[1],src[2]), dest[1] = 255; break;
CASE(4,1) dest[0]=compute_y(src[0],src[1],src[2]); break;
CASE(4,2) dest[0]=compute_y(src[0],src[1],src[2]), dest[1] = src[3]; break;
CASE(4,3) dest[0]=src[0],dest[1]=src[1],dest[2]=src[2]; break;
default: assert(0);
}
#undef CASE
}
free(data);
return good;
}
#ifndef STBI_NO_HDR
static float *ldr_to_hdr(stbi_uc *data, int x, int y, int comp)
{
int i,k,n;
float *output = (float *) malloc(x * y * comp * sizeof(float));
if (output == NULL) { free(data); return epf("outofmem", "Out of memory"); }
// compute number of non-alpha components
if (comp & 1) n = comp; else n = comp-1;
for (i=0; i < x*y; ++i) {
for (k=0; k < n; ++k) {
output[i*comp + k] = (float) pow(data[i*comp+k]/255.0f, l2h_gamma) * l2h_scale;
}
if (k < comp) output[i*comp + k] = data[i*comp+k]/255.0f;
}
free(data);
return output;
}
#define float2int(x) ((int) (x))
static stbi_uc *hdr_to_ldr(float *data, int x, int y, int comp)
{
int i,k,n;
stbi_uc *output = (stbi_uc *) malloc(x * y * comp);
if (output == NULL) { free(data); return epuc("outofmem", "Out of memory"); }
// compute number of non-alpha components
if (comp & 1) n = comp; else n = comp-1;
for (i=0; i < x*y; ++i) {
for (k=0; k < n; ++k) {
float z = (float) pow(data[i*comp+k]*h2l_scale_i, h2l_gamma_i) * 255 + 0.5f;
if (z < 0) z = 0;
if (z > 255) z = 255;
output[i*comp + k] = (uint8) float2int(z);
}
if (k < comp) {
float z = data[i*comp+k] * 255 + 0.5f;
if (z < 0) z = 0;
if (z > 255) z = 255;
output[i*comp + k] = (uint8) float2int(z);
}
}
free(data);
return output;
}
#endif
//////////////////////////////////////////////////////////////////////////////
//
// "baseline" JPEG/JFIF decoder (not actually fully baseline implementation)
//
// simple implementation
// - channel subsampling of at most 2 in each dimension
// - doesn't support delayed output of y-dimension
// - simple interface (only one output format: 8-bit interleaved RGB)
// - doesn't try to recover corrupt jpegs
// - doesn't allow partial loading, loading multiple at once
// - still fast on x86 (copying globals into locals doesn't help x86)
// - allocates lots of intermediate memory (full size of all components)
// - non-interleaved case requires this anyway
// - allows good upsampling (see next)
// high-quality
// - upsampled channels are bilinearly interpolated, even across blocks
// - quality integer IDCT derived from IJG's 'slow'
// performance
// - fast huffman; reasonable integer IDCT
// - uses a lot of intermediate memory, could cache poorly
// - load http://nothings.org/remote/anemones.jpg 3 times on 2.8Ghz P4
// stb_jpeg: 1.34 seconds (MSVC6, default release build)
// stb_jpeg: 1.06 seconds (MSVC6, processor = Pentium Pro)
// IJL11.dll: 1.08 seconds (compiled by intel)
// IJG 1998: 0.98 seconds (MSVC6, makefile provided by IJG)
// IJG 1998: 0.95 seconds (MSVC6, makefile + proc=PPro)
// huffman decoding acceleration
#define FAST_BITS 9 // larger handles more cases; smaller stomps less cache
typedef struct
{
uint8 fast[1 << FAST_BITS];
// weirdly, repacking this into AoS is a 10% speed loss, instead of a win
uint16 code[256];
uint8 values[256];
uint8 size[257];
unsigned int maxcode[18];
int delta[17]; // old 'firstsymbol' - old 'firstcode'
} huffman;
typedef struct
{
#ifdef STBI_SIMD
unsigned short dequant2[4][64];
#endif
stbi *s;
huffman huff_dc[4];
huffman huff_ac[4];
uint8 dequant[4][64];
// sizes for components, interleaved MCUs
int img_h_max, img_v_max;
int img_mcu_x, img_mcu_y;
int img_mcu_w, img_mcu_h;
// definition of jpeg image component
struct
{
int id;
int h,v;
int tq;
int hd,ha;
int dc_pred;
int x,y,w2,h2;
uint8 *data;
void *raw_data;
uint8 *linebuf;
} img_comp[4];
uint32 code_buffer; // jpeg entropy-coded buffer
int code_bits; // number of valid bits