如何以编程方式更改UIImage的色调？ [英] How to programmatically change the hue of UIImage?

问题描述

我对图像处理很新。我必须在我的iPhone应用程序项目中实现hue效果。因此，我需要更改 UIImage 的色调。请为我提供任何示例代码或教程链接。

I am very new to the image processing. I have to implement hue effect in my iPhone application project. Therefore, I need to change the hue of UIImage. Please provide me any sample code or tutorial link for this.

提前致谢

推荐答案

首先，您需要确定是将图像设为固定色调，还是旋转现有色调。两者的示例如下所示。

First, you need to decide if you are making an image a fixed hue, or rotating the existing hue. Examples of both are shown below.

可以使用标准绘图工具修复色调 - 只需确保混合模式设置为 kCGBlendModeHue ，并使用适当的色调进行绘制。这是从Nitish的解决方案中得出的，虽然我发现饱和度小于 1.0 的结果不一致。这种方法允许改变alpha，但是对于100％以外的真正饱和度，你可能需要进行第二轮绘制。

Fixing the hue can be done using the standard drawing tools - just make sure the blend mode is set to kCGBlendModeHue, and draw with the appropriate hue. This is derived from Nitish's solution, although I found that making saturation less than 1.0 had inconsistent results. This method does allow varying the alpha, but for true saturation other than 100% you will probably need a second round of drawing.

- (UIImage*) imageWithImage:(UIImage*) source fixedHue:(CGFloat) hue alpha:(CGFloat) alpha;
// Note: the hue input ranges from 0.0 to 1.0, both red.  Values outside this range will be clamped to 0.0 or 1.0.
{
    // Find the image dimensions.
    CGSize imageSize = [source size];
    CGRect imageExtent = CGRectMake(0,0,imageSize.width,imageSize.height);

    // Create a context containing the image.
    UIGraphicsBeginImageContext(imageSize);
    CGContextRef context = UIGraphicsGetCurrentContext();    
    [source drawAtPoint:CGPointMake(0,0)];

    // Draw the hue on top of the image.
    CGContextSetBlendMode(context, kCGBlendModeHue);
    [[UIColor colorWithHue:hue saturation:1.0 brightness:1 alpha:alpha] set];
    UIBezierPath *imagePath = [UIBezierPath bezierPathWithRect:imageExtent];
    [imagePath fill];

    // Retrieve the new image.
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();    

    return result;
}

旋转色调

要旋转色调，您需要Core Image滤镜。下面的代码将UIImage转换为CIImage，然后将结果转换回UIImage进行显示。根据图像的来源，您可以避免这些步骤中的一个或两个。

Rotated hue

To rotate the hue, you need Core Image filters. The code below converts the UIImage to a CIImage, and then converts the result back to UIImage for display. Depending on where your image comes from, you may be able to avoid one or both of these steps.

方便地，核心图像编程指南：使用核心图像过滤器使用CIHueAdjust过滤器。

Conveniently, the very first example in the Core Image Programming Guide: Using Core Image Filters uses the CIHueAdjust filter.

// #import <CoreImage/CoreImage.h>
// Partially from https://developer.apple.com/library/mac/#documentation/graphicsimaging/conceptual/CoreImaging/ci_tasks/ci_tasks.html
- (UIImage*) imageWithImage:(UIImage*) source rotatedByHue:(CGFloat) deltaHueRadians;
{
    // Create a Core Image version of the image.
    CIImage *sourceCore = [CIImage imageWithCGImage:[source CGImage]];

    // Apply a CIHueAdjust filter
    CIFilter *hueAdjust = [CIFilter filterWithName:@"CIHueAdjust"];
    [hueAdjust setDefaults];
    [hueAdjust setValue: sourceCore forKey: @"inputImage"];
    [hueAdjust setValue: [NSNumber numberWithFloat: deltaHueRadians] forKey: @"inputAngle"];
    CIImage *resultCore = [hueAdjust valueForKey: @"outputImage"];

    // Convert the filter output back into a UIImage.
    // This section from http://stackoverflow.com/a/7797578/1318452
    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef resultRef = [context createCGImage:resultCore fromRect:[resultCore extent]];
    UIImage *result = [UIImage imageWithCGImage:resultRef];
    CGImageRelease(resultRef);

    return result;
}

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