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我UIImage从一个创建一个NSAttributedString：

UIFont *font = [UIFont systemFontOfSize:12.0f];
NSDictionary *attributes = @{NSFontAttributeName:font,
                             NSForegroundColorAttributeName:[UIColor greenColor]};

NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:title attributes:attributes];

// Create the image here
UIImage *image = [self imageFromAttributedString:attributedString];


#pragma mark - Get image from attributed string

- (UIImage *)imageFromAttributedString:(NSAttributedString *)text
{
    UIGraphicsBeginImageContextWithOptions(text.size, NO, 0.0);

    // draw in context
    [text drawAtPoint:CGPointMake(0.0, 0.0)];

    // transfer image
    UIImage *image = [UIGraphicsGetImageFromCurrentImageContext() imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
    UIGraphicsEndImageContext();

    return image;
}

我的问题是，创建具有相同文本但“反转”的图像的最佳方法是什么，即带有白色字体文本的 [UIColor greenColor]？

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2 回答 2

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用于NSBackgroundColorAttributeName将背景设置为绿色，NSForegroundColorAttributeName将文本设置为白色。

文档包括：

NSString *const NSForegroundColorAttributeName;
NSString *const NSBackgroundColorAttributeName;

在https://developer.apple.com/library/ios/documentation/UIKit/Reference/NSAttributedString_UIKit_Additions/Reference/Reference.html#//apple_ref/doc/uid/TP40011688

于 2014-05-13T00:44:54.183 回答
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有了图像后，您可以使用 Core Image Filters 反转颜色或将蓝色更改为粉红色或红色或任何您想要的：有一个名为 CIColorInvert 的 CI 过滤器可以简单地反转颜色，但我个人更喜欢使用 colorMatrix 过滤器，它提供我要反转的更多控制代码如下：

请注意，此例程假定您的起始 UIImage 是 beginImage 输出是 endImage

使用颜色矩阵：

 CIFilter *filterci = [CIFilter filterWithName:@"CIColorMatrix"  //rgreen
                                keysAndValues: kCIInputImageKey, beginImage, nil];
[filterci setValue:[CIVector vectorWithX:-1 Y:0 Z:0 W:0] forKey:@"inputRVector"]; // 5
[filterci setValue:[CIVector vectorWithX:0 Y:-1 Z:0 W:0] forKey:@"inputGVector"]; // 6
[filterci setValue:[CIVector vectorWithX:0 Y:0 Z:-1 W:0] forKey:@"inputBVector"]; // 7
[filterci setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:1] forKey:@"inputAVector"]; // 8
[filterci setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:0] forKey:@"inputBiasVector"];     
 CIImage *boutputImagei = [filterci outputImage];

  CGImageRef cgimgi = [context createCGImage:boutputImagei fromRect:[boutputImage extent]];
UIImage *endImage = [UIImage imageWithCGImage:cgimgi];

 CGImageRelease(cgimgi);

使用 CIColorInvert：

CIFilter *filterci = [CIFilter filterWithName:@"CIColorInvert"  //rgreen
                                keysAndValues: kCIInputImageKey, beginImage, nil];
    CIImage *boutputImagei = [filterci outputImage];

  CGImageRef cgimgi = [context createCGImage:boutputImagei fromRect:[boutputImage extent]];
UIImage *endImage = [UIImage imageWithCGImage:cgimgi];

 CGImageRelease(cgimgi);
于 2014-05-13T01:15:29.410 回答