如何在不透明的UIImage[复制]上用另一种颜色替换给定的颜色

Question

我想更改不透明图像的颜色。我的原图如下：

我想把图像转换成以下格式

所以，基本上我想把图像中的红色转换成黑色（任何其他颜色）。上面两个图像是为了更好地理解而添加的。

Answer 1

注意：首先，你需要用Photoshop或任何其他工具将你的图像背景设置为透明。

然后使用下面的代码。

简单地说，您需要使用渲染模式来更改此颜色。

cokeImageView.image = [image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate]; // yourimageviewname 
[cokeImageView setTintColor:[UIColor blackColor]];

Answer 2

你可以用这个

  theImageView.image = [image  imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
   [theImageView setTintColor:[UIColor blackColor]];

Answer 3

我在“重复”上看不到任何答案（这个问题不应该被标记为重复），它可以让你用另一种颜色替换给定的颜色，并处理不透明的图像，所以我决定添加一个。

我创建了一个UIImage类别来实现这一点，它基本上是通过循环每个像素，检测它与给定颜色的接近程度，并将其与替换颜色混合（如果是）。

这将适用于具有透明和不透明背景的图像。

@implementation UIImage (UIImageColorReplacement)

-(UIImage*) imageByReplacingColor:(UIColor*)sourceColor withMinTolerance:(CGFloat)minTolerance withMaxTolerance:(CGFloat)maxTolerance withColor:(UIColor*)destinationColor {

    // components of the source color
    const CGFloat* sourceComponents = CGColorGetComponents(sourceColor.CGColor);
    UInt8* source255Components = malloc(sizeof(UInt8)*4);
    for (int i = 0; i < 4; i++) source255Components[i] = (UInt8)round(sourceComponents[i]*255.0);

    // components of the destination color
    const CGFloat* destinationComponents = CGColorGetComponents(destinationColor.CGColor);
    UInt8* destination255Components = malloc(sizeof(UInt8)*4);
    for (int i = 0; i < 4; i++) destination255Components[i] = (UInt8)round(destinationComponents[i]*255.0);

    // raw image reference
    CGImageRef rawImage = self.CGImage;

    // image attributes
    size_t width = CGImageGetWidth(rawImage);
    size_t height = CGImageGetHeight(rawImage);
    CGRect rect = {CGPointZero, {width, height}};

    // bitmap format
    size_t bitsPerComponent = 8;
    size_t bytesPerRow = width*4;
    CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;

    // data pointer
    UInt8* data = calloc(bytesPerRow, height);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // create bitmap context
    CGContextRef ctx = CGBitmapContextCreate(data, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);
    CGContextDrawImage(ctx, rect, rawImage);

    // loop through each pixel's components
    for (int byte = 0; byte < bytesPerRow*height; byte += 4) {

        UInt8 r = data[byte];
        UInt8 g = data[byte+1];
        UInt8 b = data[byte+2];

        // delta components
        UInt8 dr = abs(r-source255Components[0]);
        UInt8 dg = abs(g-source255Components[1]);
        UInt8 db = abs(b-source255Components[2]);

        // ratio of 'how far away' each component is from the source color
        CGFloat ratio = (dr+dg+db)/(255.0*3.0);
        if (ratio > maxTolerance) ratio = 1; // if ratio is too far away, set it to max.
        if (ratio < minTolerance) ratio = 0; // if ratio isn't far enough away, set it to min.

        // blend color components
        data[byte] = (UInt8)round(ratio*r)+(UInt8)round((1.0-ratio)*destination255Components[0]);
        data[byte+1] = (UInt8)round(ratio*g)+(UInt8)round((1.0-ratio)*destination255Components[1]);
        data[byte+2] = (UInt8)round(ratio*b)+(UInt8)round((1.0-ratio)*destination255Components[2]);

    }

    // get image from context
    CGImageRef img = CGBitmapContextCreateImage(ctx);

    // clean up
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);
    free(data);
    free(source255Components);
    free(destination255Components);

    UIImage* returnImage = [UIImage imageWithCGImage:img];
    CGImageRelease(img);

    return returnImage;
}

@end

用法：

UIImage* colaImage = [UIImage imageNamed:@"cola1.png"];
UIImage* blackColaImage = [colaImage imageByReplacingColor:[UIColor colorWithRed:1 green:0 blue:0 alpha:1] withMinTolerance:0.5 withMaxTolerance:0.6 withColor:[UIColor colorWithRed:0 green:0 blue:0 alpha:1]];

最小公差是像素开始与替换颜色混合（而不是被替换）的点。最大公差是像素停止混合的点。

之前：

之后：

结果是有点假，但请记住，您的原始图像相当小。这将更好地与更高分辨率的图像。你也可以利用公差来获得更好的结果！