ios 中使用blend改变图片的颜色

最新推荐文章于 2024-11-18 17:15:56 发布

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#修改图片的颜色

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本文介绍了一种通过Core Graphics中的Blend Mode技术，使用CGBlendMode枚举类型来改变按钮背景颜色的方法，避免了传统方法需要制作两张图片的繁琐过程。通过自定义UIImage类别，实现了按钮在不同状态下的背景色变化效果。

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在ios开发的过程中，我们经常会遇到这样的情况：当我们点击一个按钮时，按钮的背景颜色会发生变化，一般情况下我们会调用UIButton 的函数- (void)setBackgroundImage:(UIImage *)image forState:(UIControlState)state 来设置button在正常的情况下和按下时的背景颜色。此时我们就需要两张图片，制作图片的过程很复杂。

因此我们可以通过修改图片的背景颜色达到这样的效果：

blendMode在ios中是一个枚举类型：如下所示

enum CGBlendMode {

    kCGBlendModeNormal,
    kCGBlendModeMultiply,
    kCGBlendModeScreen,
    kCGBlendModeOverlay,
    kCGBlendModeDarken,
    kCGBlendModeLighten,
    kCGBlendModeColorDodge,
    kCGBlendModeColorBurn,
    kCGBlendModeSoftLight,
    kCGBlendModeHardLight,
    kCGBlendModeDifference,
    kCGBlendModeExclusion,
    kCGBlendModeHue,
    kCGBlendModeSaturation,
    kCGBlendModeColor,
    kCGBlendModeLuminosity,

    /* Available in Mac OS X 10.5 & later. R, S, and D are, respectively,
       premultiplied result, source, and destination colors with alpha; Ra,
       Sa, and Da are the alpha components of these colors.

       The Porter-Duff "source over" mode is called `kCGBlendModeNormal':
         R = S + D*(1 - Sa)

       Note that the Porter-Duff "XOR" mode is only titularly related to the
       classical bitmap XOR operation (which is unsupported by
       CoreGraphics). */

    kCGBlendModeClear,           /* R = 0 */
    kCGBlendModeCopy,           /* R = S */
    kCGBlendModeSourceIn,       /* R = S*Da */
    kCGBlendModeSourceOut,       /* R = S*(1 - Da) */
    kCGBlendModeSourceAtop,       /* R = S*Da + D*(1 - Sa) */
    kCGBlendModeDestinationOver,   /* R = S*(1 - Da) + D */
    kCGBlendModeDestinationIn,       /* R = D*Sa */
    kCGBlendModeDestinationOut,       /* R = D*(1 - Sa) */
    kCGBlendModeDestinationAtop,   /* R = S*(1 - Da) + D*Sa */
    kCGBlendModeXOR,           /* R = S*(1 - Da) + D*(1 - Sa) */
    kCGBlendModePlusDarker,       /* R = MAX(0, (1 - D) + (1 - S)) */
    kCGBlendModePlusLighter       /* R = MIN(1, S + D) */
};

注：premultiplied result, source, and destination colors with alpha; Ra,
Sa, and Da are the alpha components of these colors. R：表示结果 S表示包含alpha的原色， D表示含有alpha的目标色，Ra,Sa,Da分别是3个的alpja

（一）首先创建一个UIImage的类别：

@interface UIImage (Tint)

-(UIImage *)imageWithTintColor:(UIColor *)tintColor;
-(UIImage *) imageWithGradientTintClolor:(UIColor *)tintColor;

@end

（二）实现类别中的方法

//
// UIImage + Tint.m
// practice
//
// Created by user on 15/3/24.
// Copyright (c) 2015年 user. All rights reserved.
//

#import "UIImage + Tint.h"

@implementation UIImage (Tint)

-(UIImage *)imageWithTintColor:(UIColor *)tintColor blendMode: (CGBlendMode) blendMode
{
    UIGraphicsBeginImageContextWithOptions(self.size, NO,0.0f);
    [tintColor setFill];
    CGRect bounds = CGRectMake(0, 0, self.size.width, self.size.height);
    UIRectFill(bounds);
    [self drawInRect:bounds blendMode:blendMode alpha:1.0f];
    if(blendMode != kCGBlendModeDestinationIn)
    {
        [self drawInRect:bounds blendMode:kCGBlendModeDestinationIn alpha:1.0f];
    }
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    return image;
}

-(UIImage *)imageWithTintColor:(UIColor *)tintColor
{
    return [self imageWithTintColor:tintColor blendMode:kCGBlendModeDestinationIn];／／保留原图的透明度
}

-(UIImage *) imageWithGradientTintClolor:(UIColor *)tintColor
{
    return [self imageWithTintColor:tintColor blendMode:kCGBlendModeOverlay];     ／／保持背景色的明暗，就是灰暗信息
}

@end

（三）使用类别中的方法

UIImageView *imageView1 = [[UIImageView alloc]initWithFrame:CGRectMake(150, 150, 34, 34)];
    UIImageView *imageView2 = [[UIImageView alloc]initWithFrame:CGRectMake(200, 200, 34, 34)];
    UIImageView *imageView3 = [[UIImageView alloc]initWithFrame:CGRectMake(250,250, 34, 34)];

    imageView1.image = [UIImage imageNamed:@"auditing_btn_message_pre@2x.png"];

    imageView2.image = [[UIImage imageNamed:@"auditing_btn_message_pre@2x.png"] imageWithTintColor:[UIColor orangeColor]];

    imageView3.image = [[UIImage imageNamed:@"auditing_btn_message_pre@2x.png"] imageWithGradientTintClolor:[UIColor orangeColor]];

    [_firstView addSubview:imageView1];
    [_firstView addSubview:imageView2];
    [_firstView addSubview:imageView3];

程序运行之后的效果

分别是3张图片的放在视图上显示的结果