Question

我正在尝试在一些当前的UIImage（白色）上添加黑色叠加层。我一直在尝试使用以下代码：

[[UIColor blackColor] set];
[image drawAtPoint:CGPointMake(0, 0) blendMode:kCGBlendModeOverlay alpha:1.0];

但是它不起作用，而且我非常确定set不应该在那里。

Answer 1

所以，将所有答案汇总到一个这里的插入式方法可以完美地从iOS 6一直到iOS 11使用各种图像和图标：

+ (UIImage *)filledImageFrom:(UIImage *)source withColor:(UIColor *)color{

    // begin a new image context, to draw our colored image onto with the right scale
    UIGraphicsBeginImageContextWithOptions(source.size, NO, [UIScreen mainScreen].scale);

    // get a reference to that context we created
    CGContextRef context = UIGraphicsGetCurrentContext();

    // set the fill color
    [color setFill];

    // translate/flip the graphics context (for transforming from CG* coords to UI* coords
    CGContextTranslateCTM(context, 0, source.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextSetBlendMode(context, kCGBlendModeColorBurn);
    CGRect rect = CGRectMake(0, 0, source.size.width, source.size.height);
    CGContextDrawImage(context, rect, source.CGImage);

    CGContextSetBlendMode(context, kCGBlendModeSourceIn);
    CGContextAddRect(context, rect);
    CGContextDrawPath(context,kCGPathFill);

    // generate a new UIImage from the graphics context we drew onto
    UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    //return the color-burned image
    return coloredImg;
}

更新： Swift 3版

func filledImage(source: UIImage, fillColor: UIColor) -> UIImage {

    UIGraphicsBeginImageContextWithOptions(source.size, false, UIScreen.main.scale)

    let context = UIGraphicsGetCurrentContext()
    fillColor.setFill()

    context!.translateBy(x: 0, y: source.size.height)
    context!.scaleBy(x: 1.0, y: -1.0)

    context!.setBlendMode(CGBlendMode.colorBurn)
    let rect = CGRect(x: 0, y: 0, width: source.size.width, height: source.size.height)
    context!.draw(source.cgImage!, in: rect)

    context!.setBlendMode(CGBlendMode.sourceIn)
    context!.addRect(rect)
    context!.drawPath(using: CGPathDrawingMode.fill)

    let coloredImg : UIImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()

    return coloredImg
}

Answer 2

您需要将上下文剪切为图像蒙版，然后填充纯色：

- (void)drawRect:(CGRect)rect
{
    CGRect bounds = [self bounds];
    [[UIColor blackColor] set];
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextClipToMask(context, bounds, [myImage CGImage]);
    CGContextFillRect(context, bounds);
}

注意：myImage应该是包含UIImage的实例变量。我不确定它是否需要alpha通道的掩模或强度，所以请尝试两者。

Answer 3

我刚刚写了一篇有助于此的教程。我的方法为您提供了UIImage的副本，其中包含您想要的颜色变化。 rpetrich的方法很棒，但要求你创建一个子类。我的方法只是几行代码，可以放在任何需要它们的地方。 http://coffeeshopped.com/2010/09/iphone-how-to-dynamically-color-a-uiimage

NSString *name = @"badge.png";
UIImage *img = [UIImage imageNamed:name];

// begin a new image context, to draw our colored image onto
UIGraphicsBeginImageContext(img.size);

// get a reference to that context we created
CGContextRef context = UIGraphicsGetCurrentContext();

// set the fill color
[color setFill];

// translate/flip the graphics context (for transforming from CG* coords to UI* coords
CGContextTranslateCTM(context, 0, img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);

// set the blend mode to color burn, and the original image
CGContextSetBlendMode(context, kCGBlendModeColorBurn);
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
CGContextDrawImage(context, rect, img.CGImage);

// set a mask that matches the shape of the image, then draw (color burn) a colored rectangle
CGContextClipToMask(context, rect, img.CGImage);
CGContextAddRect(context, rect);
CGContextDrawPath(context,kCGPathFill);

// generate a new UIImage from the graphics context we drew onto
UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

//return the color-burned image
return coloredImg;

Answer 4

看看这个方法

 + (UIImage *)imageWithColor:(UIColor *)color andSize:(CGSize)size;
    {
      UIImage *img = nil;

      CGRect rect = CGRectMake(0, 0, size.width, size.height);
      UIGraphicsBeginImageContext(rect.size);
      CGContextRef context = UIGraphicsGetCurrentContext();
      CGContextSetFillColorWithColor(context,
                                     color.CGColor);
      CGContextFillRect(context, rect);
      img = UIGraphicsGetImageFromCurrentImageContext();

      UIGraphicsEndImageContext();

      return img;
    }

Answer 5

从iOS 7开始，有一个更简单的解决方案：

UIImage* im = [UIImage imageNamed:@"blah"];
im = [im imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
[[UIColor blackColor] setFill];
[im drawInRect:rect];

Answer 6

除了rpetrich的解决方案（顺便说一句，非常棒），你还可以用以下代码替换CGContextClipToMask行：

    CGContextSetBlendMode(context, kCGBlendModeSourceIn); //this is the main bit!

这是SourceIn混合模式，它通过GetCurrentContext中的任何内容来掩盖颜色。

Answer 7

-set用于设置后续绘图操作的颜色，不包括blits。我建议第一个电话，在UIView上显示另一个（空）UIImageView并设置其背景颜色：

myView.backgroundColor = [UIColor colorWithWhite:0.0 alpha:0.5];

显然你应该使用你想要的白色和alpha值。

Answer 8

您可以通过 Swift 4.x 以编程方式通过以下方式进行操作：

imageView.image = UIImage(named: "imageName")?.withRenderingMode(.alwaysTemplate)
imageView.tintColor = .purple

用颜色覆盖UIImage？

8 个答案: