Quartz 2D 裁剪
2013-01-08 16:30 三戒1993 阅读(155) 评论(0) 编辑 收藏 举报使用Quartz 2D 可以对图片进行裁剪,简单的可以裁剪一个矩形,复杂的可以根据CGPath实现裁剪,也可以使用UIBezierPath进行裁剪,也可以使用一个UIImage做为mask进行裁剪。
对于如下图片,不使用裁剪时,显示全部内容
使用CGContextClipToRect裁剪矩形,
- UIImage* imageSrc = [UIImage imageNamed:@"island.png"];
- CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
- CGContextRef contextRef = CGBitmapContextCreate(nil, imageSrc.size.width, imageSrc.size.height, 8, imageSrc.size.width*4, colorRef, kCGImageAlphaPremultipliedFirst);
- CGContextClipToRect(contextRef, CGRectMake(30, 100, 200, 200));
- CGContextDrawImage(contextRef, CGRectMake(0, 0, imageSrc.size.width, imageSrc.size.height), imageSrc.CGImage);
- CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
- UIImage* imageDst = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
- CGContextRelease(contextRef);
- CGColorSpaceRelease(colorRef);
- return imageDst;
结果如下:
使用CGPath 设定一个区域,然后裁剪path,
- UIImage* imageSrc = [UIImage imageNamed:@"island.png"];
- CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
- CGContextRef contextRef = CGBitmapContextCreate(nil, imageSrc.size.width, imageSrc.size.height, 8, imageSrc.size.width*4, colorRef, kCGImageAlphaPremultipliedFirst);
- //[path addCurveToPoint:CGPointMake(120, 80) controlPoint1:CGPointMake(<#CGFloat x#>, <#CGFloat y#>) controlPoint2:<#(CGPoint)#>]
- CGMutablePathRef mutPath = CGPathCreateMutable();
- CGPathMoveToPoint(mutPath, NULL, 30, 160);
- CGPathAddLineToPoint(mutPath, NULL, 120, 80);
- CGPathAddLineToPoint(mutPath, NULL, 210, 160);
- CGPathAddLineToPoint(mutPath, NULL, 120, 280);
- CGPathCloseSubpath(mutPath);
- CGContextAddPath(contextRef, mutPath);
- CGContextClip(contextRef);
- CGContextDrawImage(contextRef, CGRectMake(0, 0, imageSrc.size.width, imageSrc.size.height), imageSrc.CGImage);
- CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
- UIImage* imageDst = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
- CGContextRelease(contextRef);
- CGColorSpaceRelease(colorRef);
- return imageDst;
结果如下:
使用UIBezierPath 创建一个裁剪区域,
- UIImage* imageSrc = [UIImage imageNamed:@"island.png"];
- CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
- CGContextRef contextRef = CGBitmapContextCreate(nil, imageSrc.size.width, imageSrc.size.height, 8, imageSrc.size.width*4, colorRef, kCGImageAlphaPremultipliedFirst);
- UIBezierPath* path = [UIBezierPath bezierPath];
- [path moveToPoint:CGPointMake(30, 160)];
- // [path addCurveToPoint:CGPointMake(140, 80) controlPoint1:CGPointMake(60, 60) controlPoint2:CGPointMake(90, 60)];
- // [path addCurveToPoint:CGPointMake(210, 160) controlPoint1:CGPointMake(130, 90) controlPoint2:CGPointMake(160, 120)];
- // [path addCurveToPoint:CGPointMake(140, 280) controlPoint1:CGPointMake(180, 200) controlPoint2:CGPointMake(140, 160)];
- [path addQuadCurveToPoint:CGPointMake(140, 100) controlPoint:CGPointMake(80, 120)];
- [path addQuadCurveToPoint:CGPointMake(240, 180) controlPoint:CGPointMake(180, 100)];
- [path addQuadCurveToPoint:CGPointMake(140, 280) controlPoint:CGPointMake(210, 240)];
- [path addQuadCurveToPoint:CGPointMake(30, 160) controlPoint:CGPointMake(80, 260)];
- [path closePath];
- [path addClip];
- CGContextDrawImage(contextRef, CGRectMake(0, 0, imageSrc.size.width, imageSrc.size.height), imageSrc.CGImage);
- CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
- UIImage* imageDst = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
- CGContextRelease(contextRef);
- CGColorSpaceRelease(colorRef);
- return imageDst;
结果如下:
使用UIImage做为mask进行裁剪
使用 void CGContextClipToMask(CGContextRef c, CGRect rect, CGImageRef mask)
第一个参数表示context 指针
第二个参数表示clip到context的区域,也是mask 图片映射到context的区域
第三个参数表示mask的图片,对于裁剪区域Rect中的点是否变化取决于mask图中的alpha值,若alpha为0,则对应clip rect中的点为透明,如果alpha为1,则对应clip Rect中的点无变化。
另外CGContextClipToMask执行了类似 CGContextDrawImage 到rect区域的操作,不需要另外调用CGContextDrawImage。
例子:
下图为具有mask图片,图片中只有alpha值对于mask是有用的。
- - (UIImage*)imageWithColor:(UIColor*)color maskImage:(UIImage*)maskImage
- {
- UIImage* image = maskImage;
- CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
- CGContextRef contextRef = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, image.size.width*4, colorRef, kCGImageAlphaPremultipliedFirst);
- CGRect rect = CGRectMake(0, 0, image.size.width, image.size.height);
- CGContextClipToMask(contextRef, rect, image.CGImage);
- CGContextSetFillColorWithColor(contextRef, color.CGColor);
- CGContextFillRect(contextRef,rect);
- CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
- UIImage* imageDst = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
- CGImageRelease(imageRef);
- CGContextRelease(contextRef);
- CGColorSpaceRelease(colorRef);
- return imageDst;
- }
在DrawRect中使用上述方法后,
- - (void)drawRect:(CGRect)rect
- {
- UIImage* image1 = [UIImage imageNamed:@"cloud.png"];
- [[self imageWithColor:[UIColor redColor] maskImage:image1] drawAtPoint:CGPointMake(0, 0)];
- }
显示如下
修改maskRect区域,并为查看方便显示蓝色背景,代码如下
- - (UIImage*)imageWithColor:(UIColor*)color maskImage:(UIImage*)maskImage
- {
- UIImage* image = maskImage;
- CGColorSpaceRef colorRef = CGColorSpaceCreateDeviceRGB();
- CGContextRef contextRef = CGBitmapContextCreate(nil, image.size.width, image.size.height, 8, image.size.width*4, colorRef, kCGImageAlphaPremultipliedFirst);
- CGContextSetFillColorWithColor(contextRef, [UIColor blueColor].CGColor);
- CGRect rect = CGRectMake(0, 0, image.size.width, image.size.height);
- CGContextFillRect(contextRef,rect);
- CGRect maskRect = CGRectMake(60, 0, image.size.width, image.size.height);
- CGContextClipToMask(contextRef, maskRect, image.CGImage);
- CGContextSetFillColorWithColor(contextRef, color.CGColor);
- CGContextFillRect(contextRef,rect);
- CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
- UIImage* imageDst = [UIImage imageWithCGImage:imageRef scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp];
- CGImageRelease(imageRef);
- CGContextRelease(contextRef);
- CGColorSpaceRelease(colorRef);
- return imageDst;
- }
向右偏移60像素,结果如下