saving images

gistfile1.cpp

// uncompressed png, no dependencies
// from https://github.com/nico/hack/blob/master/wpng/wpng.c
void wpng(int w, int h, const uint8_t* pix, FILE* f) {  // pix: rgba in memory
  uint32_t crc_table[256];
  for (uint32_t n = 0, c = 0; n < 256; n++, c = n) {
    for (int k = 0; k < 8; k++) c = (c & 1) ? 0xedb88320L ^ (c >> 1) : c >> 1;
    crc_table[n] = c;
  }
#define CRCWRITE(d, len) fwrite(d, 1, len, f); for (int n = 0; n < len; n++) \
    crc = crc_table[(crc ^ (d)[n]) & 0xff] ^ (crc >> 8)
  uint8_t B[4];
#define U32BE(u) B[0] = (u) >> 24; B[1] = (u) >> 16; B[2] = (u) >> 8; B[3] = (u)
  fwrite("\x89PNG\r\n\x1a\n\0\0\0\xdIHDR", 1, 16, f);
  uint32_t crc = 0x575e51f5;  // == update_crc(0xffffffff, "IHDR")
  U32BE(w); CRCWRITE(B, 4);
  U32BE(h); CRCWRITE(B, 4);
  CRCWRITE("\x8\6\0\0\0", 5);
  U32BE(crc ^ 0xffffffff); fwrite(B, 1, 4, f); // IHDR crc32
  uint16_t scanline_size = w*4 + 1;
  U32BE(6 + (5 + scanline_size)*h); fwrite(B, 1, 4, f);
  crc = 0xffffffff;
  CRCWRITE("IDAT\x8\x1d", 6);
  uint32_t a1 = 1, a2 = 0;
  for (int y = 0; y < h; ++y, pix += w*4) {
    uint32_t s = scanline_size | (~scanline_size << 16);
    uint8_t le[] = { y == h - 1 ? 1 : 0, s, s >> 8, s >> 16, s >> 24, 0 };
    CRCWRITE(le, 6);
    CRCWRITE(pix, w*4);
    const int P = 65521;
    a2 = (a1 + a2) % P;
    for (int n = 0; n < w*4; n++) { a1 = (a1+pix[n]) % P; a2 = (a1+a2) % P; }
  }
  U32BE((a2 << 16) + a1); CRCWRITE(B, 4); // adler32 of uncompressed data
  U32BE(crc ^ 0xffffffff); fwrite(B, 1, 4, f); // IDAT crc32
#undef CRCWRITE
#undef U32BE
  fwrite("\0\0\0\0IEND\xae\x42\x60\x82", 1, 12, f);  // IEND + crc32
}


// binary pgm
// (ppm is "P6")
// drawbacks: Preview.app / chrome can't read pgm. uncompressed.
// from https://github.com/nico/hack/blob/master/cv/graymap_pgm.c
bool save_graymap_to_pgm(const char* filename, const graymap_t* graymap) {
  FILE* f = fopen(filename, "wb");
  if (!f) return false;

  const char kPgmHeader[] = "P5\n%d %d\n%d\n";
  fprintf(f, kPgmHeader, graymap->w, graymap->h, 255);
  fwrite(graymap->data, 1, graymap->w*graymap->h, f);

  fclose(f);
  return true;
}


// Any extension, using CoreGraphics
// from http://code.google.com/p/docerator/source/browse/trunk/flow.cpp
bool SaveImage(const char* name, const Img& img)
{
  bool result = true;

  CFStringRef pathString = NULL;
  CFURLRef texture_url = NULL;
  CGImageDestinationRef image_dest = NULL;
  CGImageRef image = NULL;
  CGColorSpaceRef color_space = NULL;
  CGContextRef context = NULL;
  unsigned char* dst = NULL;

  pathString = CFStringCreateWithBytes(kCFAllocatorDefault,
      (unsigned char*)name, strlen(name), kCFStringEncodingUTF8, NULL);
  texture_url = CFURLCreateWithFileSystemPath(kCFAllocatorDefault,
      pathString, kCFURLPOSIXPathStyle, FALSE);
  if (!texture_url) { result = false; goto cleanup; }

  dst = (unsigned char*)malloc(img.w * img.h * 4);
  if (img.c == 1)
    for (int y = 0; y < img.h; ++y) {
      for (int x = 0; x < img.w; ++x) {
        dst[y*img.w + x] = int(255*img.pix[y*img.w + x] + 0.5);
      }
    }
  else
    for (int y = 0; y < img.h; ++y) {
      for (int x = 0; x < img.w; ++x) {
        dst[4*(y*img.w + x) + 1] = int(255*img.pix[3*(y*img.w + x) + 0] + 0.5);
        dst[4*(y*img.w + x) + 2] = int(255*img.pix[3*(y*img.w + x) + 1] + 0.5);
        dst[4*(y*img.w + x) + 3] = int(255*img.pix[3*(y*img.w + x) + 2] + 0.5);
      }
    }

  if (img.c == 1)
    color_space = CGColorSpaceCreateDeviceGray();
  else
    color_space = CGColorSpaceCreateDeviceRGB();

  // Since icns files are always a power of two, bytes per row are always a
  // multiple of 8, as apple requires it
  context = CGBitmapContextCreate(dst, img.w, img.h,
      8, img.w * (img.c == 1 ? 1 : 4), color_space,
      img.c == 1 ? kCGImageAlphaNone : kCGImageAlphaNoneSkipFirst);

  image = CGBitmapContextCreateImage(context);
  if (!image) { result = false; goto cleanup; }

  image_dest
    = CGImageDestinationCreateWithURL(texture_url, kUTTypePNG, 1, NULL);
  if (!image_dest) { result = false; goto cleanup; }


  CGImageDestinationAddImage(image_dest, image, NULL);
  if (!CGImageDestinationFinalize(image_dest))
    result = false;

cleanup:
  if (pathString) CFRelease(pathString);
  if (context) CFRelease(context);
  if (color_space) CFRelease(color_space);
  if (image) CFRelease(image);
  if (image_dest) CFRelease(image_dest);
  if (texture_url) CFRelease(texture_url);
  if (dst) free(dst);

  assert(result);
  return result;
}


# png, using cocoa
# from https://gist.github.com/3161796
// (similar code in https://github.com/nico/hack/blob/master/cv/train_mac.m)
def saverep(rep, path):
  rep.representationUsingType_properties_(NSPNGFileType, None) \
      .writeToFile_atomically_(path, True)

def saveimg(img, path):
  s = img.size()
  img.lockFocus()
  bitmapRep = NSBitmapImageRep.alloc().initWithFocusedViewRect_(((0, 0), s))
  img.unlockFocus()
  saverep(bitmapRep, path)