[Cocoa]_[初级]_[把NSImage图片转换为灰度图片]

场景

1. 在开发Cocoa程序时, 往往需要在禁用按钮时实现一些灰度的特效, 和Windows一样, 如何实现呢?

2. NSImage有没有相关的方法呢? NSImage有一个颜色空间colorSpace的概念, 能通过转换为灰度实现吗？

说明

1. 试用灰度空间(不行), 通过NSImage的方法representations获取到NSBitmapImageRep,之后在通过bitmapImageRepByConvertingToColorSpace方法转换为新的ImageRep, 可惜报错.

NSBitmapImageRep *targetImageRep = [sourceImageRep bitmapImageRepByConvertingToColorSpace:targetColorSpace
    renderingIntent:NSColorRenderingIntentPerceptual];
return targetImageRep;


<Error>: The function `CGContextClear' is obsolete and will be removed in an upcoming update. Unfortunately, this application, or a library it uses, is using this obsolete function, and is thereby contributing to an overall degradation of system performance.

2. 通过改变图片的像素值为灰度值达到目的, 只是这种方式效率比较低.

+ (NSImage*)convertToGray:(NSImage*)image
{
    NSAutoreleasePool* pool = [NSAutoreleasePool new];
    NSBitmapImageRep* imageRep = [NSBitmapImageRep imageRepWithData:[image TIFFRepresentation]];
    for(int y = 0; y < image.size.height; ++y) {
        for(int x = 0; x < image.size.width; ++x) {
            NSColor* color = [imageRep colorAtX:x y:y];
            if([color redComponent] != 1){
                [imageRep setColor:[NSColor colorWithDeviceRed:127/255.0 green:127/255.0 blue:127/255.0 alpha:0.2] atX:x y:y];
            }
        }
    }
    NSImage* targetImage = [[NSImage alloc] initWithSize:image.size];
    [targetImage addRepresentation:imageRep];
    [pool drain];
    return targetImage;

}

3. 更好的方式？请留言

参考

NSBitmapImageRep.bitmapImageRepByConvertingToColorSpace calling deprecated CGContextClear