我怎样才能用渐变色调UIImage？

问题描述

我到处搜索但没有找到解决方案。我有图像1.我怎样才能以渐变的方式用渐变色调来获得图像2和3？以下是这些图片：

I searched everywhere but didn't find the solution. I have image 1. How can I programatically tint them with gradient to get images 2 and 3? Here are those images:

我通过Photoshop应用于它们的色调是简单的双色线性渐变。

Tints that I applied to them via Photoshop are simple 2-color linear gradients.

我的问题是：如何以编程方式实现此效果？

And my question is: how can I achieve this effect programatically?

解决方案： jrtc27给了我几乎工作示例。我修复它（对于ARC）并使其可重用（使用UIImage的类别）。这是：

Solution: jrtc27 gave me almost working example. I fixed it (for ARC) and made it reusable (using UIImage's category). Here is it:

- (UIImage *)tintedWithLinearGradientColors:(NSArray *)colorsArr {
    CGFloat scale = self.scale;
    UIGraphicsBeginImageContext(CGSizeMake(self.size.width * scale, self.size.height * scale));
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0, self.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    CGContextSetBlendMode(context, kCGBlendModeNormal);
    CGRect rect = CGRectMake(0, 0, self.size.width * scale, self.size.height * scale);
    CGContextDrawImage(context, rect, self.CGImage);

    // Create gradient

    UIColor *colorOne = [colorsArr objectAtIndex:1]; // top color
    UIColor *colorTwo = [colorsArr objectAtIndex:0]; // bottom color


    NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, (id)colorTwo.CGColor, nil];
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
    CGGradientRef gradient = CGGradientCreateWithColors(space, (__bridge CFArrayRef)colors, NULL);

    // Apply gradient

    CGContextClipToMask(context, rect, self.CGImage);
    CGContextDrawLinearGradient(context, gradient, CGPointMake(0,0), CGPointMake(0,self.size.height * scale), 0);
    UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return gradientImage;
}

推荐答案

我相信以下应该有效 - 如果没有则做评论！

I believe that the following should work - do comment if it doesn't!

// Load image
UIImage *image = [UIImage imageNamed:@"MyCoolImage.png"];
CGFloat scale = image.scale;
UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scale, image.size.height * scale));
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0, image.size.height);
CGContextScaleCTM(context, 1.0, -1.0);

CGContextSetBlendMode(context, kCGBlendModeMultiply);
CGRect rect = CGRectMake(0, 0, image.size.width * scale, image.size.height * scale);
CGContextDrawImage(context, rect, image.CGImage);

// Create gradient

UIColor *colorOne = ....;
UIColor *colorTwo = ....;

NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, (id)colorTwo.CGColor, nil];
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColors(space, (CFArrayRef)colors, NULL);

// Apply gradient

CGContextClipToMask(context, rect, image.CGImage);
CGContextDrawLinearGradient(context, gradient, CGPointMake(0,0), CGPointMake(0,image.size.height * scale), 0);
CGGradientRelease(gradient);
UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

信用获取基本想法。

这篇关于我怎样才能用渐变色调UIImage？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！