着色灰度NSImage（或CIImage） [英] Tinting a grayscale NSImage (or CIImage)

问题描述

我有一个灰度图像，我想用于绘制Cocoa控件。图像具有各种级别的灰度。在哪里是最黑的，我想要它绘制一个指定的色调最暗。

I have a grayscale image which I want to use for drawing Cocoa controls. The image has various levels of gray. Where it is darkest, I want it to draw a specified tint color darkest. I want it to be transparent where the source image is white.

基本上，我想重现在iPhone上的UINavigationBar中看到的tintColor的行为。

Basically, I want to reproduce the behavior of tintColor seen in UINavigationBar on the iPhone.

到目前为止，我已经探索了几个选项：

So far, I have explored several options:

• 使用SourceOver构图的灰度图像
  - >这需要一个不透明的着色颜色
  - >结果比期望的更暗。

• Draw the tint color over the grayscale image using SourceOver composition -> This requires a non-opaque tint color -> The result comes out much darker than desired

使用CIMultiplyCompositing CIFilter来绘制图像
- >我不能[CIImage drawAtPoint：fromRect：operation：fraction：]来仅绘制图像的一部分。同样适用于NSImage
- >偶尔出现崩溃，我不能理解

Use a CIMultiplyCompositing CIFilter to tint the image -> I can't [CIImage drawAtPoint:fromRect:operation:fraction:] to draw only part of the image. The same works fine with NSImage -> I get occasional crashes which I cannot make sense of

将灰度图像转换为掩码。也就是说黑色应该是不透明的。白色应该是透明的。灰色应该有中间alpha值。
- >这似乎是最好的解决方案
- >尝试，因为我可能，我不能实现这个。

Transform the grayscale image into a mask. I.e. Black should be opaque. White should be transparent. Gray should have intermediate alpha values. -> This would seem to be the best solution -> Try as I might, I cannot achieve this.

推荐答案

- (NSImage *)imageTintedWithColor:(NSColor *)tint 
{
    if (tint != nil) {
        NSSize size = [self size];
        NSRect bounds = { NSZeroPoint, size };
        NSImage *tintedImage = [[NSImage alloc] initWithSize:size];

        [tintedImage lockFocus];

        CIFilter *colorGenerator = [CIFilter filterWithName:@"CIConstantColorGenerator"];
        CIColor *color = [[[CIColor alloc] initWithColor:tint] autorelease];

        [colorGenerator setValue:color forKey:@"inputColor"];

        CIFilter *monochromeFilter = [CIFilter filterWithName:@"CIColorMonochrome"];
        CIImage *baseImage = [CIImage imageWithData:[self TIFFRepresentation]];

        [monochromeFilter setValue:baseImage forKey:@"inputImage"];     
        [monochromeFilter setValue:[CIColor colorWithRed:0.75 green:0.75 blue:0.75] forKey:@"inputColor"];
        [monochromeFilter setValue:[NSNumber numberWithFloat:1.0] forKey:@"inputIntensity"];

        CIFilter *compositingFilter = [CIFilter filterWithName:@"CIMultiplyCompositing"];

        [compositingFilter setValue:[colorGenerator valueForKey:@"outputImage"] forKey:@"inputImage"];
        [compositingFilter setValue:[monochromeFilter valueForKey:@"outputImage"] forKey:@"inputBackgroundImage"];

        CIImage *outputImage = [compositingFilter valueForKey:@"outputImage"];

        [outputImage drawAtPoint:NSZeroPoint
                        fromRect:bounds
                       operation:NSCompositeCopy
                        fraction:1.0];

        [tintedImage unlockFocus];  

        return [tintedImage autorelease];
    }
    else {
        return [[self copy] autorelease];
    }
}

- (NSImage*)imageCroppedToRect:(NSRect)rect
{
    NSPoint point = { -rect.origin.x, -rect.origin.y };
    NSImage *croppedImage = [[NSImage alloc] initWithSize:rect.size];

    [croppedImage lockFocus];
    {
        [self compositeToPoint:point operation:NSCompositeCopy];
    }
    [croppedImage unlockFocus];

    return [croppedImage autorelease];
}

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