iOS：将RGB滤镜应用于灰度PNG [英] iOS: Applying a RGB filter to a greyscale PNG

问题描述

（PNG格式，所以有alpha分量）

我有一个灰度gem顶视图。

我想从这个图像创建12个小尺寸的按钮，每个按钮都有不同的颜色。

为了整洁，我想在代码中做这个，而不是在外部在一些艺术包。

任何人都可以提供一个方法（甚至一些代码）做到这一点？

PS我知道如何在GL中使用一个荒谬的数量的代码，我希望有一个更简单的方式使用核心图形/核心动画编辑：b
$ b

编辑：工作解决方案，感谢从下面的精彩回答

  CGSize targetSize =（CGSize）{100,100}; 
 UIImage * image; 
 {
 CGRect rect =（CGRect）{.size = targetSize}; 
 
 UIGraphicsBeginImageContext（targetSize）; 
 {
 CGContextRef X = UIGraphicsGetCurrentContext（）; 
 
 UIImage * uiGem = [UIImage imageNamed：@GemTop_Dull.png]; 
 
 //绘制宝石
 [uiGem drawInRect：rect]; 
 
 //覆盖一个红色的矩形
 CGContextSetBlendMode（X，kCGBlendModeColor）; 
 CGContextSetRGBFillColor（X，0.9，0，0，1）; 
 CGContextFillRect（X，rect）; 
 
 //重画宝石
 [uiGem drawInRect：rect 
 blendMode：kCGBlendModeDestinationIn 
 alpha：1.]; 
 
 image = UIGraphicsGetImageFromCurrentImageContext（）; 
} 
 UIGraphicsEndImageContext（）; 
 
  

解决方案

最简单的方法是将图像绘制成RGB颜色空间的 CGBitmapContext ，使用 CGContextSetBlendMode 设置 kCGBlendModeColor ，然后用纯色绘制它（例如用 CGContextFillRect ）。

I have a greyscale gem top view.

(PNG format, so has alpha component)

I would like to create 12 small size buttons, each in a different colour, from this image.

For the sake of tidiness, I would like to do this within the code rather than externally in some art package.

Can anyone provide a method (or even some code) for doing this?

PS I am aware of how to do it in GL using a ridiculous amount of code, I'm hoping there is a simpler way using core graphics / core animation

EDIT: Working solution, thanks to awesomeness from below answer

    CGSize targetSize = (CGSize){100,100};
    UIImage* image;
    {
        CGRect rect = (CGRect){ .size = targetSize };

        UIGraphicsBeginImageContext( targetSize );
        {
            CGContextRef X = UIGraphicsGetCurrentContext();

            UIImage* uiGem = [UIImage imageNamed: @"GemTop_Dull.png"];

            // draw gem
            [uiGem drawInRect: rect];

            // overlay a red rectangle
            CGContextSetBlendMode( X, kCGBlendModeColor ) ;
            CGContextSetRGBFillColor ( X,  0.9, 0, 0,  1 );
            CGContextFillRect ( X, rect );

            // redraw gem 
            [uiGem drawInRect: rect
                    blendMode: kCGBlendModeDestinationIn
                        alpha: 1. ];

            image = UIGraphicsGetImageFromCurrentImageContext();
        }
        UIGraphicsEndImageContext();
    }

解决方案

The easiest way to do it is to draw the image into an RGB-colorspaced CGBitmapContext, use CGContextSetBlendMode to set kCGBlendModeColor, and then draw over it with a solid color (e.g. with CGContextFillRect).

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