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Merge branch 'stbiw-png-compr' of https://github.com/DanielGibson/stb

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This commit is contained in:
Sean Barrett 2018-01-29 02:53:25 -08:00
commit 9de22e5a70
1 changed files with 29 additions and 5 deletions
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34
stb_image_write.h
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@ -16,16 +16,22 @@ ABOUT:
adapted to write to memory or a general streaming interface; let me know.
The PNG output is not optimal; it is 20-50% larger than the file
written by a decent optimizing implementation. This library is designed
for source code compactness and simplicity, not optimal image file size
or run-time performance.
written by a decent optimizing implementation; though providing a custom
zlib compress function (see STBIW_ZLIB_COMPRESS) can mitigate that.
This library is designed for source code compactness and simplicity,
not optimal image file size or run-time performance.
BUILDING:
You can #define STBIW_ASSERT(x) before the #include to avoid using assert.h.
You can #define STBIW_MALLOC(), STBIW_REALLOC(), and STBIW_FREE() to replace
malloc,realloc,free.
You can define STBIW_MEMMOVE() to replace memmove()
You can #define STBIW_MEMMOVE() to replace memmove()
You can #define STBIW_ZLIB_COMPRESS to use a custom zlib-style compress function
for PNG compression (instead of the builtin one), it must have the following signature:
unsigned char * my_compress(unsigned char *data, int data_len, int *out_len, int quality);
The returned data will be freed with STBIW_FREE() (free() by default),
so it must be heap allocated with STBIW_MALLOC() (malloc() by default),
USAGE:
@ -77,6 +83,9 @@ USAGE:
writer, both because it is in BGR order and because it may have padding
at the end of the line.)
PNG allows you to set the deflate compression level by setting the global
variable 'stbi_write_png_level' (it defaults to 8).
HDR expects linear float data. Since the format is always 32-bit rgb(e)
data, alpha (if provided) is discarded, and for monochrome data it is
replicated across all three channels.
@ -135,6 +144,7 @@ extern "C" {
#else
#define STBIWDEF extern
extern int stbi_write_tga_with_rle;
extern int stbi_write_png_level;
#endif
#ifndef STBI_WRITE_NO_STDIO
@ -686,6 +696,7 @@ STBIWDEF int stbi_write_hdr(char const *filename, int x, int y, int comp, const
// PNG writer
//
#ifndef STBIW_ZLIB_COMPRESS
// stretchy buffer; stbiw__sbpush() == vector<>::push_back() -- stbiw__sbcount() == vector<>::size()
#define stbiw__sbraw(a) ((int *) (a) - 2)
#define stbiw__sbm(a) stbiw__sbraw(a)[0]
@ -766,8 +777,14 @@ static unsigned int stbiw__zhash(unsigned char *data)
#define stbiw__ZHASH 16384
#endif // STBIW_ZLIB_COMPRESS
unsigned char * stbi_zlib_compress(unsigned char *data, int data_len, int *out_len, int quality)
{
#ifdef STBIW_ZLIB_COMPRESS
// user provided a zlib compress implementation, use that
return STBIW_ZLIB_COMPRESS(data, data_len, out_len, quality);
#else // use builtin
static unsigned short lengthc[] = { 3,4,5,6,7,8,9,10,11,13,15,17,19,23,27,31,35,43,51,59,67,83,99,115,131,163,195,227,258, 259 };
static unsigned char lengtheb[]= { 0,0,0,0,0,0,0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0 };
static unsigned short distc[] = { 1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,257,385,513,769,1025,1537,2049,3073,4097,6145,8193,12289,16385,24577, 32768 };
@ -869,6 +886,7 @@ unsigned char * stbi_zlib_compress(unsigned char *data, int data_len, int *out_l
// make returned pointer freeable
STBIW_MEMMOVE(stbiw__sbraw(out), out, *out_len);
return (unsigned char *) stbiw__sbraw(out);
#endif // STBIW_ZLIB_COMPRESS
}
static unsigned int stbiw__crc32(unsigned char *buffer, int len)
@ -934,6 +952,12 @@ static unsigned char stbiw__paeth(int a, int b, int c)
return STBIW_UCHAR(c);
}
#ifdef STB_IMAGE_WRITE_STATIC
static int stbi_write_png_level = 8;
#else
int stbi_write_png_level = 8;
#endif
// @OPTIMIZE: provide an option that always forces left-predict or paeth predict
unsigned char *stbi_write_png_to_mem(unsigned char *pixels, int stride_bytes, int x, int y, int n, int *out_len)
{
@ -989,7 +1013,7 @@ unsigned char *stbi_write_png_to_mem(unsigned char *pixels, int stride_bytes, in
STBIW_MEMMOVE(filt+j*(x*n+1)+1, line_buffer, x*n);
}
STBIW_FREE(line_buffer);
zlib = stbi_zlib_compress(filt, y*( x*n+1), &zlen, 8); // increase 8 to get smaller but use more memory
zlib = stbi_zlib_compress(filt, y*( x*n+1), &zlen, stbi_write_png_level);
STBIW_FREE(filt);
if (!zlib) return 0;