stb_image_write.h

/* stbiw-0.92 - public domain - http://nothings.org/stb/stb_image_write.h
   writes out PNG/BMP/TGA images to C stdio - Sean Barrett 2010
                            no warranty implied; use at your own risk


Before including,

    #define STB_IMAGE_WRITE_IMPLEMENTATION

in the file that you want to have the implementation.


ABOUT:

   This header file is a library for writing images to C stdio. It could be
   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 simplicitly, not optimal image file size
   or run-time performance.

USAGE:

   There are three functions, one for each image file format:

     int stbi_write_png(char const *filename, int w, int h, int comp, const void *data, int stride_in_bytes);
     int stbi_write_bmp(char const *filename, int w, int h, int comp, const void *data);
     int stbi_write_tga(char const *filename, int w, int h, int comp, const void *data);

   Each function returns 0 on failure and non-0 on success.
   
   The functions create an image file defined by the parameters. The image
   is a rectangle of pixels stored from left-to-right, top-to-bottom.
   Each pixel contains 'comp' channels of data stored interleaved with 8-bits
   per channel, in the following order: 1=Y, 2=YA, 3=RGB, 4=RGBA. (Y is
   monochrome color.) The rectangle is 'w' pixels wide and 'h' pixels tall.
   The *data pointer points to the first byte of the top-left-most pixel.
   For PNG, "stride_in_bytes" is the distance in bytes from the first byte of
   a row of pixels to the first byte of the next row of pixels.

   PNG creates output files with the same number of components as the input.
   The BMP and TGA formats expand Y to RGB in the file format. BMP does not
   output alpha.
   
   PNG supports writing rectangles of data even when the bytes storing rows of
   data are not consecutive in memory (e.g. sub-rectangles of a larger image),
   by supplying the stride between the beginning of adjacent rows. The other
   formats do not. (Thus you cannot write a native-format BMP through the BMP
   writer, both because it is in BGR order and because it may have padding
   at the end of the line.)
*/

#ifndef INCLUDE_STB_IMAGE_WRITE_H
#define INCLUDE_STB_IMAGE_WRITE_H

#ifdef __cplusplus
extern "C" {
#endif

extern int stbi_write_png(char const *filename, int w, int h, int comp, const void *data, int stride_in_bytes);
extern int stbi_write_bmp(char const *filename, int w, int h, int comp, const void *data);
extern int stbi_write_tga(char const *filename, int w, int h, int comp, const void *data);

#ifdef __cplusplus
}
#endif

#endif//INCLUDE_STB_IMAGE_WRITE_H

#ifdef STB_IMAGE_WRITE_IMPLEMENTATION

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>

typedef unsigned int stbiw_uint32;
typedef int stb_image_write_test[sizeof(stbiw_uint32)==4 ? 1 : -1];

static void writefv(FILE *f, const char *fmt, va_list v)
{
   while (*fmt) {
      switch (*fmt++) {
         case ' ': break;
         case '1': { unsigned char x = (unsigned char) va_arg(v, int); fputc(x,f); break; }
         case '2': { int x = va_arg(v,int); unsigned char b[2];
                     b[0] = (unsigned char) x; b[1] = (unsigned char) (x>>8);
                     fwrite(b,2,1,f); break; }
         case '4': { stbiw_uint32 x = va_arg(v,int); unsigned char b[4];
                     b[0]=(unsigned char)x; b[1]=(unsigned char)(x>>8);
                     b[2]=(unsigned char)(x>>16); b[3]=(unsigned char)(x>>24);
                     fwrite(b,4,1,f); break; }
         default:
            assert(0);
            return;
      }
   }
}

static void write3(FILE *f, unsigned char a, unsigned char b, unsigned char c)
{
   unsigned char arr[3];
   arr[0] = a, arr[1] = b, arr[2] = c;
   fwrite(arr, 3, 1, f);
}

static void write_pixels(FILE *f, int rgb_dir, int vdir, int x, int y, int comp, void *data, int write_alpha, int scanline_pad)
{
   unsigned char bg[3] = { 255, 0, 255}, px[3];
   stbiw_uint32 zero = 0;
   int i,j,k, j_end;

   if (y <= 0)
      return;

   if (vdir < 0) 
      j_end = -1, j = y-1;
   else
      j_end =  y, j = 0;

   for (; j != j_end; j += vdir) {
      for (i=0; i < x; ++i) {
         unsigned char *d = (unsigned char *) data + (j*x+i)*comp;
         if (write_alpha < 0)
            fwrite(&d[comp-1], 1, 1, f);
         switch (comp) {
            case 1:
            case 2: write3(f, d[0],d[0],d[0]);
                    break;
            case 4:
               if (!write_alpha) {
                  // composite against pink background
                  for (k=0; k < 3; ++k)
                     px[k] = bg[k] + ((d[k] - bg[k]) * d[3])/255;
                  write3(f, px[1-rgb_dir],px[1],px[1+rgb_dir]);
                  break;
               }
               /* FALLTHROUGH */
            case 3:
               write3(f, d[1-rgb_dir],d[1],d[1+rgb_dir]);
               break;
         }
         if (write_alpha > 0)
            fwrite(&d[comp-1], 1, 1, f);
      }
      fwrite(&zero,scanline_pad,1,f);
   }
}

static int outfile(char const *filename, int rgb_dir, int vdir, int x, int y, int comp, void *data, int alpha, int pad, const char *fmt, ...)
{
   FILE *f;
   if (y < 0 || x < 0) return 0;
   f = fopen(filename, "wb");
   if (f) {
      va_list v;
      va_start(v, fmt);
      writefv(f, fmt, v);
      va_end(v);
      write_pixels(f,rgb_dir,vdir,x,y,comp,data,alpha,pad);
      fclose(f);
   }
   return f != NULL;
}

int stbi_write_bmp(char const *filename, int x, int y, int comp, const void *data)
{
   int pad = (-x*3) & 3;
   return outfile(filename,-1,-1,x,y,comp,(void *) data,0,pad,
           "11 4 22 4" "4 44 22 444444",
           'B', 'M', 14+40+(x*3+pad)*y, 0,0, 14+40,  // file header
            40, x,y, 1,24, 0,0,0,0,0,0);             // bitmap header
}

int stbi_write_tga(char const *filename, int x, int y, int comp, const void *data)
{
   int has_alpha = !(comp & 1);
   return outfile(filename, -1,-1, x, y, comp, (void *) data, has_alpha, 0,
                  "111 221 2222 11", 0,0,2, 0,0,0, 0,0,x,y, 24+8*has_alpha, 8*has_alpha);
}

// stretchy buffer; stbi__sbpush() == vector<>::push_back() -- stbi__sbcount() == vector<>::size()
#define stbi__sbraw(a) ((int *) (a) - 2)
#define stbi__sbm(a)   stbi__sbraw(a)[0]
#define stbi__sbn(a)   stbi__sbraw(a)[1]

#define stbi__sbneedgrow(a,n)  ((a)==0 || stbi__sbn(a)+n >= stbi__sbm(a))
#define stbi__sbmaybegrow(a,n) (stbi__sbneedgrow(a,(n)) ? stbi__sbgrow(a,n) : 0)
#define stbi__sbgrow(a,n)  stbi__sbgrowf((void **) &(a), (n), sizeof(*(a)))

#define stbi__sbpush(a, v)      (stbi__sbmaybegrow(a,1), (a)[stbi__sbn(a)++] = (v))
#define stbi__sbcount(a)        ((a) ? stbi__sbn(a) : 0)
#define stbi__sbfree(a)         ((a) ? free(stbi__sbraw(a)),0 : 0)

static void *stbi__sbgrowf(void **arr, int increment, int itemsize)
{
   int m = *arr ? 2*stbi__sbm(*arr)+increment : increment+1;
   void *p = realloc(*arr ? stbi__sbraw(*arr) : 0, itemsize * m + sizeof(int)*2);
   assert(p);
   if (p) {
      if (!*arr) ((int *) p)[1] = 0;
      *arr = (void *) ((int *) p + 2);
      stbi__sbm(*arr) = m;
   }
   return *arr;
}

static unsigned char *stbi__zlib_flushf(unsigned char *data, unsigned int *bitbuffer, int *bitcount)
{
   while (*bitcount >= 8) {
      stbi__sbpush(data, (unsigned char) *bitbuffer);
      *bitbuffer >>= 8;
      *bitcount -= 8;
   }
   return data;
}

static int stbi__zlib_bitrev(int code, int codebits)
{
   int res=0;
   while (codebits--) {
      res = (res << 1) | (code & 1);
      code >>= 1;
   }
   return res;
}

static unsigned int stbi__zlib_countm(unsigned char *a, unsigned char *b, int limit)
{
   int i;
   for (i=0; i < limit && i < 258; ++i)
      if (a[i] != b[i]) break;
   return i;
}

static unsigned int stbi__zhash(unsigned char *data)
{
   stbiw_uint32 hash = data[0] + (data[1] << 8) + (data[2] << 16);
   hash ^= hash << 3;
   hash += hash >> 5;
   hash ^= hash << 4;
   hash += hash >> 17;
   hash ^= hash << 25;
   hash += hash >> 6;
   return hash;
}

#define stbi__zlib_flush() (out = stbi__zlib_flushf(out, &bitbuf, &bitcount))
#define stbi__zlib_add(code,codebits) \
      (bitbuf |= (code) << bitcount, bitcount += (codebits), stbi__zlib_flush())
#define stbi__zlib_huffa(b,c)  stbi__zlib_add(stbi__zlib_bitrev(b,c),c)
// default huffman tables
#define stbi__zlib_huff1(n)  stbi__zlib_huffa(0x30 + (n), 8)
#define stbi__zlib_huff2(n)  stbi__zlib_huffa(0x190 + (n)-144, 9)
#define stbi__zlib_huff3(n)  stbi__zlib_huffa(0 + (n)-256,7)
#define stbi__zlib_huff4(n)  stbi__zlib_huffa(0xc0 + (n)-280,8)
#define stbi__zlib_huff(n)  ((n) <= 143 ? stbi__zlib_huff1(n) : (n) <= 255 ? stbi__zlib_huff2(n) : (n) <= 279 ? stbi__zlib_huff3(n) : stbi__zlib_huff4(n))
#define stbi__zlib_huffb(n) ((n) <= 143 ? stbi__zlib_huff1(n) : stbi__zlib_huff2(n))

#define stbi__ZHASH   16384

unsigned char * stbi_zlib_compress(unsigned char *data, int data_len, int *out_len, int quality)
{
   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 };
   static unsigned char  disteb[]  = { 0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13 };
   unsigned int bitbuf=0;
   int i,j, bitcount=0;
   unsigned char *out = NULL;
   unsigned char **hash_table[stbi__ZHASH]; // 64KB on the stack!
   if (quality < 5) quality = 5;

   stbi__sbpush(out, 0x78);   // DEFLATE 32K window
   stbi__sbpush(out, 0x5e);   // FLEVEL = 1
   stbi__zlib_add(1,1);  // BFINAL = 1
   stbi__zlib_add(1,2);  // BTYPE = 1 -- fixed huffman

   for (i=0; i < stbi__ZHASH; ++i)
      hash_table[i] = NULL;

   i=0;
   while (i < data_len-3) {
      // hash next 3 bytes of data to be compressed 
      int h = stbi__zhash(data+i)&(stbi__ZHASH-1), best=3;
      unsigned char *bestloc = 0;
      unsigned char **hlist = hash_table[h];
      int n = stbi__sbcount(hlist);
      for (j=0; j < n; ++j) {
         if (hlist[j]-data > i-32768) { // if entry lies within window
            int d = stbi__zlib_countm(hlist[j], data+i, data_len-i);
            if (d >= best) best=d,bestloc=hlist[j];
         }
      }
      // when hash table entry is too long, delete half the entries
      if (hash_table[h] && stbi__sbn(hash_table[h]) == 2*quality) {
         memcpy(hash_table[h], hash_table[h]+quality, sizeof(hash_table[h][0])*quality);
         stbi__sbn(hash_table[h]) = quality;
      }
      stbi__sbpush(hash_table[h],data+i);

      if (bestloc) {
         // "lazy matching" - check match at *next* byte, and if it's better, do cur byte as literal
         h = stbi__zhash(data+i+1)&(stbi__ZHASH-1);
         hlist = hash_table[h];
         n = stbi__sbcount(hlist);
         for (j=0; j < n; ++j) {
            if (hlist[j]-data > i-32767) {
               int e = stbi__zlib_countm(hlist[j], data+i+1, data_len-i-1);
               if (e > best) { // if next match is better, bail on current match
                  bestloc = NULL;
                  break;
               }
            }
         }
      }

      if (bestloc) {
         int d = data+i - bestloc; // distance back
         assert(d <= 32767 && best <= 258);
         for (j=0; best > lengthc[j+1]-1; ++j);
         stbi__zlib_huff(j+257);
         if (lengtheb[j]) stbi__zlib_add(best - lengthc[j], lengtheb[j]);
         for (j=0; d > distc[j+1]-1; ++j);
         stbi__zlib_add(stbi__zlib_bitrev(j,5),5);
         if (disteb[j]) stbi__zlib_add(d - distc[j], disteb[j]);
         i += best;
      } else {
         stbi__zlib_huffb(data[i]);
         ++i;
      }
   }
   // write out final bytes
   for (;i < data_len; ++i)
      stbi__zlib_huffb(data[i]);
   stbi__zlib_huff(256); // end of block
   // pad with 0 bits to byte boundary
   while (bitcount)
      stbi__zlib_add(0,1);

   for (i=0; i < stbi__ZHASH; ++i)
      (void) stbi__sbfree(hash_table[i]);

   {
      // compute adler32 on input
      unsigned int i=0, s1=1, s2=0, blocklen = data_len % 5552;
      int j=0;
      while (j < data_len) {
         for (i=0; i < blocklen; ++i) s1 += data[j+i], s2 += s1;
         s1 %= 65521, s2 %= 65521;
         j += blocklen;
         blocklen = 5552;
      }
      stbi__sbpush(out, (unsigned char) (s2 >> 8));
      stbi__sbpush(out, (unsigned char) s2);
      stbi__sbpush(out, (unsigned char) (s1 >> 8));
      stbi__sbpush(out, (unsigned char) s1);
   }
   *out_len = stbi__sbn(out);
   // make returned pointer freeable
   memmove(stbi__sbraw(out), out, *out_len);
   return (unsigned char *) stbi__sbraw(out);
}

unsigned int stbi__crc32(unsigned char *buffer, int len)
{
   static unsigned int crc_table[256];
   unsigned int crc = ~0u;
   int i,j;
   if (crc_table[1] == 0)
      for(i=0; i < 256; i++)
         for (crc_table[i]=i, j=0; j < 8; ++j)
            crc_table[i] = (crc_table[i] >> 1) ^ (crc_table[i] & 1 ? 0xedb88320 : 0);
   for (i=0; i < len; ++i)
      crc = (crc >> 8) ^ crc_table[buffer[i] ^ (crc & 0xff)];
   return ~crc;
}

#define stbi__wpng4(o,a,b,c,d) ((o)[0]=(unsigned char)(a),(o)[1]=(unsigned char)(b),(o)[2]=(unsigned char)(c),(o)[3]=(unsigned char)(d),(o)+=4)
#define stbi__wp32(data,v) stbi__wpng4(data, (v)>>24,(v)>>16,(v)>>8,(v));
#define stbi__wptag(data,s) stbi__wpng4(data, s[0],s[1],s[2],s[3])

static void stbi__wpcrc(unsigned char **data, int len)
{
   unsigned int crc = stbi__crc32(*data - len - 4, len+4);
   stbi__wp32(*data, crc);
}

static unsigned char stbi__paeth(int a, int b, int c)
{
   int p = a + b - c, pa = abs(p-a), pb = abs(p-b), pc = abs(p-c);
   if (pa <= pb && pa <= pc) return (unsigned char) a;
   if (pb <= pc) return (unsigned char) b;
   return (unsigned char) c;
}

unsigned char *stbi_write_png_to_mem(unsigned char *pixels, int stride_bytes, int x, int y, int n, int *out_len)
{
   int ctype[5] = { -1, 0, 4, 2, 6 };
   unsigned char sig[8] = { 137,80,78,71,13,10,26,10 };
   unsigned char *out,*o, *filt, *zlib;
   signed char *line_buffer;
   int i,j,k,p,zlen;

   if (stride_bytes == 0)
      stride_bytes = x * n;

   filt = (unsigned char *) malloc((x*n+1) * y); if (!filt) return 0;
   line_buffer = (signed char *) malloc(x * n); if (!line_buffer) { free(filt); return 0; }
   for (j=0; j < y; ++j) {
      static int mapping[] = { 0,1,2,3,4 };
      static int firstmap[] = { 0,1,0,5,6 };
      int *mymap = j ? mapping : firstmap;
      int best = 0, bestval = 0x7fffffff;
      for (p=0; p < 2; ++p) {
         for (k= p?best:0; k < 5; ++k) {
            int type = mymap[k],est=0;
            unsigned char *z = pixels + stride_bytes*j;
            for (i=0; i < n; ++i)
               switch (type) {
                  case 0: line_buffer[i] = z[i]; break;
                  case 1: line_buffer[i] = z[i]; break;
                  case 2: line_buffer[i] = z[i] - z[i-stride_bytes]; break;
                  case 3: line_buffer[i] = z[i] - (z[i-stride_bytes]>>1); break;
                  case 4: line_buffer[i] = (signed char) (z[i] - stbi__paeth(0,z[i-stride_bytes],0)); break;
                  case 5: line_buffer[i] = z[i]; break;
                  case 6: line_buffer[i] = z[i]; break;
               }
            for (i=n; i < x*n; ++i) {
               switch (type) {
                  case 0: line_buffer[i] = z[i]; break;
                  case 1: line_buffer[i] = z[i] - z[i-n]; break;
                  case 2: line_buffer[i] = z[i] - z[i-stride_bytes]; break;
                  case 3: line_buffer[i] = z[i] - ((z[i-n] + z[i-stride_bytes])>>1); break;
                  case 4: line_buffer[i] = z[i] - stbi__paeth(z[i-n], z[i-stride_bytes], z[i-stride_bytes-n]); break;
                  case 5: line_buffer[i] = z[i] - (z[i-n]>>1); break;
                  case 6: line_buffer[i] = z[i] - stbi__paeth(z[i-n], 0,0); break;
               }
            }
            if (p) break;
            for (i=0; i < x*n; ++i)
               est += abs((signed char) line_buffer[i]);
            if (est < bestval) { bestval = est; best = k; }
         }
      }
      // when we get here, best contains the filter type, and line_buffer contains the data
      filt[j*(x*n+1)] = (unsigned char) best;
      memcpy(filt+j*(x*n+1)+1, line_buffer, x*n);
   }
   free(line_buffer);
   zlib = stbi_zlib_compress(filt, y*( x*n+1), &zlen, 8); // increase 8 to get smaller but use more memory
   free(filt);
   if (!zlib) return 0;

   // each tag requires 12 bytes of overhead
   out = (unsigned char *) malloc(8 + 12+13 + 12+zlen + 12); 
   if (!out) return 0;
   *out_len = 8 + 12+13 + 12+zlen + 12;

   o=out;
   memcpy(o,sig,8); o+= 8;
   stbi__wp32(o, 13); // header length
   stbi__wptag(o, "IHDR");
   stbi__wp32(o, x);
   stbi__wp32(o, y);
   *o++ = 8;
   *o++ = (unsigned char) ctype[n];
   *o++ = 0;
   *o++ = 0;
   *o++ = 0;
   stbi__wpcrc(&o,13);

   stbi__wp32(o, zlen);
   stbi__wptag(o, "IDAT");
   memcpy(o, zlib, zlen); o += zlen; free(zlib);
   stbi__wpcrc(&o, zlen);

   stbi__wp32(o,0);
   stbi__wptag(o, "IEND");
   stbi__wpcrc(&o,0);

   assert(o == out + *out_len);

   return out;
}

int stbi_write_png(char const *filename, int x, int y, int comp, const void *data, int stride_bytes)
{
   FILE *f;
   int len;
   unsigned char *png = stbi_write_png_to_mem((unsigned char *) data, stride_bytes, x, y, comp, &len);
   if (!png) return 0;
   f = fopen(filename, "wb");
   if (!f) { free(png); return 0; }
   fwrite(png, 1, len, f);
   fclose(f);
   free(png);
   return 1;
}
#endif // STB_IMAGE_WRITE_IMPLEMENTATION

/* Revision history

      0.92 (2010-08-01)
             casts to unsigned char to fix warnings
      0.91 (2010-07-17)
             first public release
      0.90   first internal release
*/