ios - 尝试替换所有白色时 UIImage 背景中的奇怪颜色

Question

我的应用程序中有一个选项可以更改按钮的颜色。我使用 UIImage 上的一个类别来做到这一点。我不想用某种颜色对按钮进行着色/刻录，而是用存储在 NSUserDefaults 中的颜色替换所有白色（255、255、255）像素。该按钮是一个具有透明背景的随机播放图标。它看起来像这样，白色替换为红色：

我创建了我的代码：http ://brandontreb.com/image-manipulation-retrieving-and-updating-pixel-values-for-a-uiimage 这是我用来替换像素的代码。我把它放在我的 UIImage 类别中：

-(UIImage *)replaceWhiteWith{
    NSString *str = [[NSUserDefaults standardUserDefaults] objectForKey:@"color"];
    UIColor *color = [NSString colorFromNSString:str];
    return [self replaceWithColor:color];
}

-(UIImage *) replaceWithColor:(UIColor *)color {
    CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha =0.0;
    [color getRed:&red green:&green blue:&blue alpha:&alpha];
    CGContextRef ctx;
    CGImageRef imageRef = [self CGImage];
    NSUInteger width = CGImageGetWidth(imageRef);
    NSUInteger height = CGImageGetHeight(imageRef);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = malloc(height * width * 4);
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                                 bitsPerComponent, bytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
    CGContextRelease(context);

    int byteIndex = 0;
    for (int ii = 0 ; ii < width * height ; ++ii)
    {
        if(rawData[byteIndex] == 255 && rawData[byteIndex+1] == 255  && rawData[byteIndex+2] == 255){
            rawData[byteIndex] = (red) * 255;
            rawData[byteIndex+1] = (green) * 255;
            rawData[byteIndex+2] = (blue) * 255;
            rawData[byteIndex+3] = (alpha) * 255;
        }

        byteIndex += 4;
    }


    ctx = CGBitmapContextCreate(rawData,
                                CGImageGetWidth( imageRef ),
                                CGImageGetHeight( imageRef ),
                                8,
                                CGImageGetBytesPerRow( imageRef ),
                                CGImageGetColorSpace( imageRef ),
                                kCGImageAlphaPremultipliedLast );

    imageRef = CGBitmapContextCreateImage (ctx);
    UIImage* rawImage = [UIImage imageWithCGImage:imageRef];

    CGContextRelease(ctx);

    return rawImage;
}

Answer 1

使用不同的代码，我在循环中滑过，它不再显示随机背景静态：

-(UIImage *)replaceWhiteWith{
    NSString *str = [[NSUserDefaults standardUserDefaults] objectForKey:@"color"];
    UIColor *color = [NSString colorFromNSString:str];
    CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha =0.0;
    [color getRed:&red green:&green blue:&blue alpha:&alpha];
    CGImageRef inImage = self.CGImage;
    CFDataRef ref = CGDataProviderCopyData(CGImageGetDataProvider(inImage));
    UInt8 * buf = (UInt8 *) CFDataGetBytePtr(ref);
    int length = CFDataGetLength(ref);

    for(int i=0; i<length; i+=4)
    {
        int r = buf[i];
        int g = buf[i+1];
        int b = buf[i+2];
        if(r == 255 && g == 255  && b == 255){
            buf[i] = ((red) * 255);
            buf[i+1] = ((green) * 255);
            buf[i+2] = ((blue) * 255);
        }
    }

    CGContextRef ctx = CGBitmapContextCreate(buf,
                                             CGImageGetWidth(inImage),
                                             CGImageGetHeight(inImage),
                                             CGImageGetBitsPerComponent(inImage),
                                             CGImageGetBytesPerRow(inImage),
                                             CGImageGetColorSpace(inImage),
                                             CGImageGetAlphaInfo(inImage));

    CGImageRef img = CGBitmapContextCreateImage(ctx);
    CFRelease(ref);
    CGContextRelease(ctx);
    return [UIImage imageWithCGImage:img];
}