mcap/modules/Image_Decode/imageio.jai

// ImageIO, macOS's own codecs: HEIC and AVIF, WebP, TIFF and the camera RAW formats, as WIC reads them
// on Windows. Only the few Core Foundation, ImageIO and Core Graphics calls used are declared.

// The primary image in bytes, as non-premultiplied RGBA (default allocator), as stored: not turned.
// orientation is what ImageIO says the image's orientation is (1-8, from a HEIF's irot and imir, or
// its EXIF), for image_decode to apply where exif.jai cannot read it.
//
// The pixels keep the image's own RGB color space, as WIC and stb_image leave them; only gray, CMYK
// and the like are converted, to sRGB.
imageio_decode :: (bytes: [] u8) -> Image, ok: bool, error: string, orientation: s64 {
  image: Image;
  // Not copied: the source is let go of before this returns.
  data := CFDataCreateWithBytesNoCopy(null, bytes.data, bytes.count, kCFAllocatorNull);
  if !data  return image, false, "ImageIO could not take the bytes", 1;
  defer CFRelease(data);

  source := CGImageSourceCreateWithData(data, null);
  if !source  return image, false, "ImageIO cannot read it", 1;
  defer CFRelease(source);
  if CGImageSourceGetCount(source) < 1  return image, false, "ImageIO finds no image in it", 1;

  index := CGImageSourceGetPrimaryImageIndex(source);
  cg := CGImageSourceCreateImageAtIndex(source, index, null);
  if !cg  return image, false, "ImageIO cannot decode it", 1;
  defer CGImageRelease(cg);

  orientation: s32 = 1;
  properties := CGImageSourceCopyPropertiesAtIndex(source, index, null);
  if properties {
    number := CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
    if number  CFNumberGetValue(number, kCFNumberSInt32Type, *orientation);
    CFRelease(properties);
  }

  w := CGImageGetWidth(cg);
  h := CGImageGetHeight(cg);
  if !w || !h  return image, false, "ImageIO gives it no size", orientation;
  if w * h * 4 > U32_MAX  return image, false, tprint("it is % x %, too large to decode in one piece", w, h), orientation;

  // Opaque images are drawn as 8-bit RGB with the fourth byte left out, so their pixels are exact.
  // Others are drawn premultiplied, the only RGBA a bitmap context takes, at 16 bits a channel so
  // that dividing back gives the 8-bit colors again, even where alpha is small.
  alpha_info := CGImageGetAlphaInfo(cg);
  opaque := alpha_info == kCGImageAlphaNone || alpha_info == kCGImageAlphaNoneSkipLast || alpha_info == kCGImageAlphaNoneSkipFirst;
  bits: u64 = 16;
  bitmap_info: u32 = kCGBitmapByteOrder16Little | kCGImageAlphaPremultipliedLast;
  if opaque { bits = 8; bitmap_info = kCGBitmapByteOrder32Big | kCGImageAlphaNoneSkipLast; }
  row_bytes := w * bits / 2;

  count := cast(s64) (w * h);
  pixels := cast(*u8) alloc(count * 4,, context.default_allocator);
  drawn := pixels;
  if !opaque  drawn = cast(*u8) alloc(count * 8,, context.default_allocator);
  defer if drawn != pixels  free(drawn,, context.default_allocator);
  memset(drawn, 0, cast(s64) (row_bytes * h));

  space := CGImageGetColorSpace(cg);
  own_space := space && CGColorSpaceGetModel(space) == kCGColorSpaceModelRGB;
  bitmap: CGContextRef;
  if own_space  bitmap = CGBitmapContextCreate(drawn, w, h, bits, row_bytes, space, bitmap_info);
  if !bitmap {
    // Not RGB, or a space a bitmap context cannot draw in (an extended range one): converted to sRGB.
    srgb := CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
    defer CGColorSpaceRelease(srgb);
    bitmap = CGBitmapContextCreate(drawn, w, h, bits, row_bytes, srgb, bitmap_info);
  }
  if !bitmap {
    free(pixels,, context.default_allocator);
    return image, false, "Core Graphics could not make a bitmap to draw it in", orientation;
  }
  CGContextSetBlendMode(bitmap, kCGBlendModeCopy);
  CGContextDrawImage(bitmap, .{.{0, 0}, .{cast(float64) w, cast(float64) h}}, cg);
  CGContextRelease(bitmap);

  if opaque {
    for 0..count - 1  pixels[it * 4 + 3] = 255;
  } else {
    wide := cast(*u16) drawn;
    for 0..count - 1 {
      in  := wide + it * 4;
      out := pixels + it * 4;
      a := cast(u32) in[3];
      out[3] = cast(u8) ((a * 255 + 32767) / 65535);
      if a == 0 { out[0], out[1], out[2] = 0; continue; }
      for c: 0..2  out[c] = cast(u8) min(255, (cast(u32) in[c] * 255 + a / 2) / a);
    }
  }
  image = .{pixels = pixels, width = cast(s32) w, height = cast(s32) h};
  return image, true, "", orientation;
}

#scope_file

CFTypeRef        :: *void;
CFDataRef        :: *void;
CFDictionaryRef  :: *void;
CFStringRef      :: *void;
CFAllocatorRef   :: *void;
CGImageSourceRef :: *void;
CGImageRef       :: *void;
CGColorSpaceRef  :: *void;
CGContextRef     :: *void;

CGPoint :: struct { x, y: float64; }
CGSize  :: struct { width, height: float64; }
CGRect  :: struct { origin: CGPoint; size: CGSize; }

kCFNumberSInt32Type :: 3;
kCGColorSpaceModelRGB :: 1;
kCGBlendModeCopy :: 17;

kCGImageAlphaNone               :: 0;
kCGImageAlphaPremultipliedLast  :: 1;
kCGImageAlphaNoneSkipLast       :: 5;
kCGImageAlphaNoneSkipFirst      :: 6;
kCGBitmapByteOrder16Little :: 1 << 12;
kCGBitmapByteOrder32Big    :: 4 << 12;

CoreFoundation :: #library,system "CoreFoundation";
ImageIO        :: #library,system "ImageIO";
CoreGraphics   :: #library,system "CoreGraphics";

kCFAllocatorNull:            CFAllocatorRef #elsewhere CoreFoundation;
kCGImagePropertyOrientation: CFStringRef    #elsewhere ImageIO;
kCGColorSpaceSRGB:           CFStringRef    #elsewhere CoreGraphics;

CFDataCreateWithBytesNoCopy :: (allocator: CFAllocatorRef, bytes: *u8, length: s64, deallocator: CFAllocatorRef) -> CFDataRef #foreign CoreFoundation;
CFRelease                   :: (object: CFTypeRef) #foreign CoreFoundation;
CFDictionaryGetValue        :: (dictionary: CFDictionaryRef, key: *void) -> *void #foreign CoreFoundation;
CFNumberGetValue            :: (number: *void, type: s64, value: *void) -> u8 #foreign CoreFoundation;

CGImageSourceCreateWithData        :: (data: CFDataRef, options: CFDictionaryRef) -> CGImageSourceRef #foreign ImageIO;
CGImageSourceGetCount              :: (source: CGImageSourceRef) -> u64 #foreign ImageIO;
CGImageSourceGetPrimaryImageIndex  :: (source: CGImageSourceRef) -> u64 #foreign ImageIO;
CGImageSourceCreateImageAtIndex    :: (source: CGImageSourceRef, index: u64, options: CFDictionaryRef) -> CGImageRef #foreign ImageIO;
CGImageSourceCopyPropertiesAtIndex :: (source: CGImageSourceRef, index: u64, options: CFDictionaryRef) -> CFDictionaryRef #foreign ImageIO;

CGImageGetWidth          :: (image: CGImageRef) -> u64 #foreign CoreGraphics;
CGImageGetHeight         :: (image: CGImageRef) -> u64 #foreign CoreGraphics;
CGImageGetAlphaInfo      :: (image: CGImageRef) -> u32 #foreign CoreGraphics;
CGImageGetColorSpace     :: (image: CGImageRef) -> CGColorSpaceRef #foreign CoreGraphics;
CGImageRelease           :: (image: CGImageRef) #foreign CoreGraphics;
CGColorSpaceGetModel     :: (space: CGColorSpaceRef) -> s32 #foreign CoreGraphics;
CGColorSpaceCreateWithName :: (name: CFStringRef) -> CGColorSpaceRef #foreign CoreGraphics;
CGColorSpaceRelease      :: (space: CGColorSpaceRef) #foreign CoreGraphics;
CGBitmapContextCreate    :: (data: *void, width: u64, height: u64, bits_per_component: u64, bytes_per_row: u64, space: CGColorSpaceRef, bitmap_info: u32) -> CGContextRef #foreign CoreGraphics;
CGContextSetBlendMode    :: (context_ref: CGContextRef, mode: s32) #foreign CoreGraphics;
CGContextDrawImage       :: (context_ref: CGContextRef, rect: CGRect, image: CGImageRef) #foreign CoreGraphics;
CGContextRelease         :: (context_ref: CGContextRef) #foreign CoreGraphics;