我已经设法通过使用 NSBitmapImageRep 获得了我想要的东西（通过一些 hack 访问它）。如果有人知道这样做的更好方法，请分享。
- (NSBitmapImageRep)bitmap 方法是我的 hack。NSImage 开始时只有一个 NSBitmapImageRep，但是在旋转方法之后添加了一个 CIImageRep，它优先于破坏颜色代码的 NSBitmapImageRep（因为 NSImage 呈现不着色的 CIImageRep）。
BitmapImage.m（NSImage 的子类）
CGContextRef CreateARGBBitmapContext (CGImageRef inImage)
{
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
size_t pixelsWide = CGImageGetWidth(inImage);
size_t pixelsHigh = CGImageGetHeight(inImage);
bitmapBytesPerRow = (int)(pixelsWide * 4);
bitmapByteCount = (int)(bitmapBytesPerRow * pixelsHigh);
colorSpace = CGColorSpaceCreateDeviceRGB();
if (colorSpace == NULL)
return nil;
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
CGColorSpaceRelease( colorSpace );
return nil;
}
context = CGBitmapContextCreate (bitmapData,
pixelsWide,
pixelsHigh,
8,
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedFirst);
if (context == NULL)
{
free (bitmapData);
fprintf (stderr, "Context not created!");
}
CGColorSpaceRelease( colorSpace );
return context;
}
- (NSData *)RGB565Data
{
CGContextRef cgctx = CreateARGBBitmapContext(self.CGImage);
if (cgctx == NULL)
return nil;
size_t w = CGImageGetWidth(self.CGImage);
size_t h = CGImageGetHeight(self.CGImage);
CGRect rect = {{0,0},{w,h}};
CGContextDrawImage(cgctx, rect, self.CGImage);
void *data = CGBitmapContextGetData (cgctx);
CGContextRelease(cgctx);
if (!data)
return nil;
vImage_Buffer src;
src.data = data;
src.width = w;
src.height = h;
src.rowBytes = (w * 4);
void* destData = malloc((w * 2) * h);
vImage_Buffer dst;
dst.data = destData;
dst.width = w;
dst.height = h;
dst.rowBytes = (w * 2);
vImageConvert_ARGB8888toRGB565(&src, &dst, 0);
size_t dataSize = 2 * w * h; // RGB565 = 2 5-bit components and 1 6-bit (16 bits/2 bytes)
NSData *RGB565Data = [NSData dataWithBytes:dst.data length:dataSize];
free(destData);
return RGB565Data;
}
- (NSBitmapImageRep*)bitmap
{
NSBitmapImageRep *bitmap = nil;
NSMutableArray *repsToRemove = [NSMutableArray array];
// Iterate through the representations that back the NSImage
for (NSImageRep *rep in self.representations)
{
// If the representation is a bitmap
if ([rep isKindOfClass:[NSBitmapImageRep class]])
{
bitmap = [(NSBitmapImageRep*)rep retain];
break;
}
else
{
[repsToRemove addObject:rep];
}
}
// If no bitmap representation was found, we create one (this shouldn't occur)
if (bitmap == nil)
{
bitmap = [[[NSBitmapImageRep alloc] initWithCGImage:self.CGImage] retain];
[self addRepresentation:bitmap];
}
for (NSImageRep *rep2 in repsToRemove)
{
[self removeRepresentation:rep2];
}
return [bitmap autorelease];
}
- (NSColor*)colorAtX:(NSInteger)x y:(NSInteger)y
{
return [self.bitmap colorAtX:x y:y];
}
- (void)setColor:(NSColor*)color atX:(NSInteger)x y:(NSInteger)y
{
[self.bitmap setColor:color atX:x y:y];
}
NSImage+Extra.m（NSImage 类别）
- (CGImageRef)CGImage
{
return [self CGImageForProposedRect:NULL context:[NSGraphicsContext currentContext] hints:nil];
}
用法
- (IBAction)load:(id)sender
{
NSOpenPanel* openDlg = [NSOpenPanel openPanel];
[openDlg setCanChooseFiles:YES];
[openDlg setCanChooseDirectories:YES];
if ( [openDlg runModalForDirectory:nil file:nil] == NSOKButton )
{
NSArray* files = [openDlg filenames];
for( int i = 0; i < [files count]; i++ )
{
NSString* fileName = [files objectAtIndex:i];
BitmapImage *image = [[BitmapImage alloc] initWithContentsOfFile:fileName];
imageView.image = image;
}
}
}
- (IBAction)colorize:(id)sender
{
float width = imageView.image.size.width;
float height = imageView.image.size.height;
BitmapImage *img = (BitmapImage*)imageView.image;
NSColor *newColor = [img colorAtX:1 y:1];
for (int x = 0; x <= width; x++)
{
for (int y = 0; y <= height; y++)
{
if ([img colorAtX:x y:y] == newColor)
{
[img setColor:[NSColor redColor] atX:x y:y];
}
}
}
[imageView setNeedsDisplay:YES];
}
- (IBAction)rotate:(id)sender
{
BitmapImage *img = (BitmapImage*)imageView.image;
BitmapImage *newImg = [img rotate90DegreesClockwise:NO];
imageView.image = newImg;
}
编辑（2013 年 4 月 24 日）
我更改了以下代码：
- (RGBColor)colorAtX:(NSInteger)x y:(NSInteger)y
{
NSUInteger components[4];
[self.bitmap getPixel:components atX:x y:y];
//NSLog(@"R: %ld, G:%ld, B:%ld", components[0], components[1], components[2]);
RGBColor color = {components[0], components[1], components[2]};
return color;
}
- (BOOL)color:(RGBColor)a isEqualToColor:(RGBColor)b
{
return ((a.red == b.red) && (a.green == b.green) && (a.blue == b.blue));
}
- (void)setColor:(RGBColor)color atX:(NSUInteger)x y:(NSUInteger)y
{
NSUInteger components[4] = {(NSUInteger)color.red, (NSUInteger)color.green, (NSUInteger)color.blue, 255};
//NSLog(@"R: %ld, G: %ld, B: %ld", components[0], components[1], components[2]);
[self.bitmap setPixel:components atX:x y:y];
}
- (IBAction)colorize:(id)sender
{
float width = imageView.image.size.width;
float height = imageView.image.size.height;
BitmapImage *img = (BitmapImage*)imageView.image;
RGBColor oldColor = [img colorAtX:0 y:0];
RGBColor newColor;// = {255, 0, 0};
newColor.red = 255;
newColor.green = 0;
newColor.blue = 0;
for (int x = 0; x <= width; x++)
{
for (int y = 0; y <= height; y++)
{
if ([img color:[img colorAtX:x y:y] isEqualToColor:oldColor])
{
[img setColor:newColor atX:x y:y];
}
}
}
[imageView setNeedsDisplay:YES];
}
但现在它在第一次调用 colorize 方法时将像素变为红色，然后变为蓝色。
编辑 2 (24/04/2013)
下面的代码修复了它。这是因为旋转代码为 NSBitmapImageRep 添加了一个 alpha 通道。
- (RGBColor)colorAtX:(NSInteger)x y:(NSInteger)y
{
if (self.bitmap.hasAlpha)
{
NSUInteger components[4];
[self.bitmap getPixel:components atX:x y:y];
RGBColor color = {components[1], components[2], components[3]};
return color;
}
else
{
NSUInteger components[3];
[self.bitmap getPixel:components atX:x y:y];
RGBColor color = {components[0], components[1], components[2]};
return color;
}
}
- (void)setColor:(RGBColor)color atX:(NSUInteger)x y:(NSUInteger)y
{
if (self.bitmap.hasAlpha)
{
NSUInteger components[4] = {255, (NSUInteger)color.red, (NSUInteger)color.green, (NSUInteger)color.blue};
[self.bitmap setPixel:components atX:x y:y];
}
else
{
NSUInteger components[3] = {color.red, color.green, color.blue};
[self.bitmap setPixel:components atX:x y:y];
}
}