154在屏幕中绘图时设置透明度（扩展知识：为图片视图添加点击手势识别器，来实现点击事件操作）...
2024-05-31 08:52:35
一张图片，通过混合模式绘制后，能得到不同效果的图片。
这里的示例仅是测试效果；实际上可以通过不同程度的混合模式绘制，来得到符合需求的效果。
效果如下：
ViewController.h
1 #import <UIKit/UIKit.h> 2 3 @interface ViewController : UIViewController 4 @property (strong, nonatomic) UIImageView *imgVBlend; 5 @property (strong, nonatomic) UILabel *lblMsg; 6 7 @end
ViewController.m
1 #import "ViewController.h"
2 #import "UIImage+BlendMode.h"
3
4 @interface ViewController ()
5 - (void)layoutUI;
6 - (void)changeBlendMode;
7 @end
8
9 @implementation ViewController
10 #define kImgBlend [UIImage imageNamed:@"ImageForBlend"]
11
12 - (void)viewDidLoad {
13 [super viewDidLoad];
14
15 [self layoutUI];
16 }
17
18 - (void)didReceiveMemoryWarning {
19 [super didReceiveMemoryWarning];
20 // Dispose of any resources that can be recreated.
21 }
22
23 - (void)layoutUI {
24 //添加图片视图_imgVBlend
25 CGPoint newPoint = self.view.center;
26 _imgVBlend = [[UIImageView alloc] initWithImage:kImgBlend];
27 _imgVBlend.center = newPoint;
28 //在允许进行用户交互操作前提下，通过为图片视图_imgVBlend添加点击手势识别器，来实现点击事件操作
29 _imgVBlend.userInteractionEnabled = YES; //设置是否允许进行用户交互操作；默认值为NO
30 UITapGestureRecognizer *gesture = [[UITapGestureRecognizer alloc] initWithTarget:self
31 action:@selector(changeBlendMode)];
32 gesture.numberOfTouchesRequired = 1; //设置触摸手指数；默认值为1
33 gesture.numberOfTapsRequired = 1; //设置点击数；默认值为1，表示单击
34 [_imgVBlend addGestureRecognizer:gesture];
35 [self.view addSubview:_imgVBlend];
36
37 //添加标签_lblMsg
38 _lblMsg = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width - 40, 120)];
39 newPoint.y += 144;
40 _lblMsg.center = newPoint;
41 _lblMsg.numberOfLines = 0;
42 _lblMsg.text = @"在屏幕中绘图时设置透明度；点击图片切换为混合模式绘制的图片";
43 _lblMsg.textAlignment = NSTextAlignmentLeft;
44 _lblMsg.textColor = [UIColor blackColor];
45 _lblMsg.layer.borderColor = [UIColor grayColor].CGColor;
46 _lblMsg.layer.borderWidth = 1.0;
47 [self.view addSubview:_lblMsg];
48
49
50 // enum CGBlendMode {
51 // /* Available in Mac OS X 10.4 & later. */
52 // kCGBlendModeNormal,
53 // kCGBlendModeMultiply,
54 // kCGBlendModeScreen,
55 // kCGBlendModeOverlay,
56 // kCGBlendModeDarken,
57 // kCGBlendModeLighten,
58 // kCGBlendModeColorDodge,
59 // kCGBlendModeColorBurn,
60 // kCGBlendModeSoftLight,
61 // kCGBlendModeHardLight,
62 // kCGBlendModeDifference,
63 // kCGBlendModeExclusion,
64 // kCGBlendModeHue,
65 // kCGBlendModeSaturation,
66 // kCGBlendModeColor,
67 // kCGBlendModeLuminosity,
68 //
69 // /* Available in Mac OS X 10.5 & later. R, S, and D are, respectively,
70 // premultiplied result, source, and destination colors with alpha; Ra,
71 // Sa, and Da are the alpha components of these colors.
72 //
73 // The Porter-Duff "source over" mode is called `kCGBlendModeNormal':
74 // R = S + D*(1 - Sa)
75 //
76 // Note that the Porter-Duff "XOR" mode is only titularly related to the
77 // classical bitmap XOR operation (which is unsupported by
78 // CoreGraphics). */
79 //
80 // kCGBlendModeClear, /* R = 0 */
81 // kCGBlendModeCopy, /* R = S */
82 // kCGBlendModeSourceIn, /* R = S*Da */
83 // kCGBlendModeSourceOut, /* R = S*(1 - Da) */
84 // kCGBlendModeSourceAtop, /* R = S*Da + D*(1 - Sa) */
85 // kCGBlendModeDestinationOver, /* R = S*(1 - Da) + D */
86 // kCGBlendModeDestinationIn, /* R = D*Sa */
87 // kCGBlendModeDestinationOut, /* R = D*(1 - Sa) */
88 // kCGBlendModeDestinationAtop, /* R = S*(1 - Da) + D*Sa */
89 // kCGBlendModeXOR, /* R = S*(1 - Da) + D*(1 - Sa) */
90 // kCGBlendModePlusDarker, /* R = MAX(0, (1 - D) + (1 - S)) */
91 // kCGBlendModePlusLighter /* R = MIN(1, S + D) */
92 // };
93 // typedef enum CGBlendMode CGBlendMode; /* Available in Mac OS X 10.4 & later. */
94 }
95
96 - (void)changeBlendMode {
97 static CGBlendMode blendMode = kCGBlendModeNormal;
98 NSString *strMsg;
99 switch (blendMode) {
100 case kCGBlendModeNormal: {
101 strMsg = @"kCGBlendModeNormal: 正常；也是默认的模式。前景图会覆盖背景图";
102 break;
103 }
104 case kCGBlendModeMultiply: {
105 strMsg = @"kCGBlendModeMultiply: 正片叠底；混合了前景和背景的颜色，最终颜色比原先的都暗";
106 break;
107 }
108 case kCGBlendModeScreen: {
109 strMsg = @"kCGBlendModeScreen: 滤色；把前景和背景图的颜色先反过来，然后混合";
110 break;
111 }
112 case kCGBlendModeOverlay: {
113 strMsg = @"kCGBlendModeOverlay: 覆盖；能保留灰度信息，结合kCGBlendModeSaturation能保留透明度信息，在imageWithBlendMode方法中两次执行drawInRect方法实现我们基本需求";
114 break;
115 }
116 case kCGBlendModeDarken: {
117 strMsg = @"kCGBlendModeDarken: 变暗";
118 break;
119 }
120 case kCGBlendModeLighten: {
121 strMsg = @"kCGBlendModeLighten: 变亮";
122 break;
123 }
124 case kCGBlendModeColorDodge: {
125 strMsg = @"kCGBlendModeColorDodge: 颜色变淡";
126 break;
127 }
128 case kCGBlendModeColorBurn: {
129 strMsg = @"kCGBlendModeColorBurn: 颜色加深";
130 break;
131 }
132 case kCGBlendModeSoftLight: {
133 strMsg = @"kCGBlendModeSoftLight: 柔光";
134 break;
135 }
136 case kCGBlendModeHardLight: {
137 strMsg = @"kCGBlendModeHardLight: 强光";
138 break;
139 }
140 case kCGBlendModeDifference: {
141 strMsg = @"kCGBlendModeDifference: 插值";
142 break;
143 }
144 case kCGBlendModeExclusion: {
145 strMsg = @"kCGBlendModeExclusion: 排除";
146 break;
147 }
148 case kCGBlendModeHue: {
149 strMsg = @"kCGBlendModeHue: 色调";
150 break;
151 }
152 case kCGBlendModeSaturation: {
153 strMsg = @"kCGBlendModeSaturation: 饱和度";
154 break;
155 }
156 case kCGBlendModeColor: {
157 strMsg = @"kCGBlendModeColor: 颜色";
158 break;
159 }
160 case kCGBlendModeLuminosity: {
161 strMsg = @"kCGBlendModeLuminosity: 亮度";
162 break;
163 }
164 //Apple额外定义的枚举
165 //R: premultiplied result, 表示混合结果
166 //S: Source, 表示源颜色(Sa对应透明度值: 0.0-1.0)
167 //D: destination colors with alpha, 表示带透明度的目标颜色(Da对应透明度值: 0.0-1.0)
168 case kCGBlendModeClear: {
169 strMsg = @"kCGBlendModeClear: R = 0";
170 break;
171 }
172 case kCGBlendModeCopy: {
173 strMsg = @"kCGBlendModeCopy: R = S";
174 break;
175 }
176 case kCGBlendModeSourceIn: {
177 strMsg = @"kCGBlendModeSourceIn: R = S*Da";
178 break;
179 }
180 case kCGBlendModeSourceOut: {
181 strMsg = @"kCGBlendModeSourceOut: R = S*(1 - Da)";
182 break;
183 }
184 case kCGBlendModeSourceAtop: {
185 strMsg = @"kCGBlendModeSourceAtop: R = S*Da + D*(1 - Sa)";
186 break;
187 }
188 case kCGBlendModeDestinationOver: {
189 strMsg = @"kCGBlendModeDestinationOver: R = S*(1 - Da) + D";
190 break;
191 }
192 case kCGBlendModeDestinationIn: {
193 strMsg = @"kCGBlendModeDestinationIn: R = D*Sa；能保留透明度信息";
194 break;
195 }
196 case kCGBlendModeDestinationOut: {
197 strMsg = @"kCGBlendModeDestinationOut: R = D*(1 - Sa)";
198 break;
199 }
200 case kCGBlendModeDestinationAtop: {
201 strMsg = @"kCGBlendModeDestinationAtop: R = S*(1 - Da) + D*Sa";
202 break;
203 }
204 case kCGBlendModeXOR: {
205 strMsg = @"kCGBlendModeXOR: R = S*(1 - Da) + D*(1 - Sa)";
206 break;
207 }
208 case kCGBlendModePlusDarker: {
209 strMsg = @"kCGBlendModePlusDarker: R = MAX(0, (1 - D) + (1 - S))";
210 break;
211 }
212 case kCGBlendModePlusLighter: {
213 strMsg = @"kCGBlendModePlusLighter: R = MIN(1, S + D)（最后一种混合模式）";
214 break;
215 }
216 default: {
217 break;
218 }
219 }
220 _imgVBlend.image = [kImgBlend imageWithBlendMode:blendMode tintColor:[UIColor orangeColor]]; //使用分类Category来扩展UIImage，添加自定义实例方法imageWithBlendMode
221 _lblMsg.text = strMsg;
222
223 blendMode++;
224 if (blendMode > kCGBlendModePlusLighter) {
225 blendMode = kCGBlendModeNormal;
226 }
227 }
228
229 @endUIImage+BlendMode.h
1 #import <UIKit/UIKit.h> 2 3 @interface UIImage (BlendMode) 4 - (UIImage *)imageWithBlendMode:(CGBlendMode)blendMode tintColor:(UIColor *)tintColor; 5 6 @end
UIImage+BlendMode.m
1 #import "UIImage+BlendMode.h"
2
3 @implementation UIImage (BlendMode)
4
5 - (UIImage *)imageWithBlendMode:(CGBlendMode)blendMode tintColor:(UIColor *)tintColor {
6 UIImage *img;
7 UIGraphicsBeginImageContextWithOptions(self.size, NO, 0); //开始图片上下文绘制
8
9 [tintColor setFill]; //填充颜色
10 CGRect newRect = CGRectMake(0, 0, self.size.width, self.size.height);
11 UIRectFill(newRect);
12 [self drawInRect:newRect blendMode:blendMode alpha:1.0]; //设置绘画透明混合模式和透明度
13 if (blendMode == kCGBlendModeOverlay) {
14 [self drawInRect:newRect blendMode:kCGBlendModeDestinationIn alpha:1.0]; //能保留透明度信息
15 }
16
17 img = UIGraphicsGetImageFromCurrentImageContext();
18
19 UIGraphicsEndImageContext(); //结束图片上下文绘制
20 return img;
21 }
22
23 @end转载于:https://www.cnblogs.com/huangjianwu/p/4581509.html
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