ios中实现图片的裁剪

转自:http://blog.sina.com.cn/s/blog_6084f58801013n34.html

现在打算做一个拼图游戏，游戏引擎用cocos2d。先说一下设计要求，支持从相册或相机所拍照片中导入图片，导入的图片往往不符合我们的要求，这时就需要我们进行图片的裁剪

如图所示，当用户对图片进行缩放，移动变换后，最终把方框中的图片裁剪出来作为拼图游戏中的图片素材。先说一下前部中空四周半透明UIImage的绘制方式，直接上代码：

// draw the front image

- (UIImageView *)frontView{

    CGSize winSize=CGSizeMake(1024, 768);

   

    UIImageView * fView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 0, winSize.width, winSize.height)];

   

    CGColorSpaceRefcolorSpace = CGColorSpaceCreateDeviceRGB();

   

    // 1. create the context, reverse it upside down; after the translate, origin is at top-left corner

    CGContextRef context = CGBitmapContextCreate(NULL, winSize.width, winSize.height, 8, 4 * winSize.width, colorSpace, kCGImageAlphaPremultipliedFirst);

   

    CGContextSaveGState(context);

    CGContextBeginPath(context);

   

    CGContextMoveToPoint(context, 0, 0);

    CGContextAddLineToPoint(context, winSize.width, 0);

    CGContextAddLineToPoint(context, winSize.width, winSize.height);

    CGContextAddLineToPoint(context, 0, winSize.height);

    CGContextAddLineToPoint(context, 0, 0);

   

   

    CGContextMoveToPoint(context, winSize.width*0.2, winSize.height*0.2);

    CGContextAddLineToPoint(context, winSize.width*0.8, winSize.height*0.2);

    CGContextAddLineToPoint(context, winSize.width*0.8, winSize.height*0.8);

    CGContextAddLineToPoint(context, winSize.width*0.2, winSize.height*0.8);

    CGContextAddLineToPoint(context, winSize.width*0.2, winSize.height*0.2);

   

    CGContextClosePath(context);

    CGContextSetRGBFillColor(context, 0.6,0.6, 0.6, 0.6);

    CGContextEOFillPath(context);

    CGContextRestoreGState(context);

   

    // get the image

    CGImageRef largeImageMasked = CGBitmapContextCreateImage(context);

   

    // 5. get only the specific region

    CGImageRef imageMasked = CGImageCreateWithImageInRect(largeImageMasked, CGRectMake(0, 0, winSize.width, winSize.height));

    CGImageRelease(largeImageMasked);

    CGContextRelease(context);

   

    UIImage * newImage = [UIImageimageWithCGImage:imageMasked];

    CGImageRelease(imageMasked);

 

    fView.image=newImage;

    [fView sizeToFit];

    return [fView autorelease];

}

 

 

 

 

这次到重点了，就是图片的裁剪。

下面为裁剪部分的代码

 

- (void)clipBtnClicked:(id)sender{

   

    CGSize winSize=[[CCDirector sharedDirector] winSize];

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGSize imageSize=[[_imageView image] size];

    // 1. create the context, reverse it upside down; after the translate, origin is at top-left corner

    CGContextRef context = CGBitmapContextCreate(NULL, imageSize.width, imageSize.height, 8, 4 * imageSize.width, colorSpace, kCGImageAlphaPremultipliedFirst);

    CGContextSaveGState(context);

    CGContextDrawImage(context, CGRectMake(0,0,imageSize.width,imageSize.height),_imageView.image.CGImage);

    CGContextRestoreGState(context);

    

    //imageScale

    float scale=_imageView.frame.size.width/imageSize.width;

    CGSize clipSize=CGSizeMake(winSize.width*0.6/scale, winSize.height*0.6/scale);

    //offset from center

    CGPoint offset=ccpSub(ccp(_imageView.frame.origin.x,_imageView.frame.origin.y+_imageView.frame.size.height),ccp(winSize.width*0.2,winSize.height*0.8));

    offset=ccp(-offset.x,offset.y/scale);

    CGContextSaveGState(context);

    CGContextBeginPath(context);

    CGContextMoveToPoint(context, offset.x, offset.y);

    CGContextAddLineToPoint(context, offset.x, offset.y+clipSize.height);

    CGContextAddLineToPoint(context, offset.x+clipSize.width, offset.y+clipSize.height);

    CGContextAddLineToPoint(context, offset.x+clipSize.width, offset.y);

    CGContextAddLineToPoint(context, offset.x, offset.y);

    CGContextClosePath(context);

    CGContextRestoreGState(context);

    

    CGContextSaveGState(context);

    CGContextSetRGBFillColor(context, 1, 0, 0, 0.2);

    CGContextFillPath(context);

    CGContextRestoreGState(context);

    

    

    // stroke

    CGContextSetStrokeColorSpace(context, colorSpace);

    CGFloat strokeColor[4]    = {1.0,0,0,1.0};

    CGContextSetStrokeColor(context, strokeColor);

    CGContextSetLineWidth(context, 4);

    CGContextStrokePath(context);

    

    // get the image

    CGImageRef largeImageMasked = CGBitmapContextCreateImage(context);

    

    CGPoint offset2=ccpSub(ccp(_imageView.frame.origin.x,_imageView.frame.origin.y),ccp(winSize.width*0.2,winSize.height*0.2));

    offset2=ccp(-offset2.x,-offset2.y/scale);

   // 5. get only the specific region

    CGImageRef imageMasked = CGImageCreateWithImageInRect(largeImageMasked,CGRectMake(offset2.x,offset2.y, clipSize.width, clipSize.height));

    CGImageRelease(largeImageMasked);

    //CGImageRef imageMasked = largeImageMasked;

    CGContextRelease(context);

    

    UIImage* newImage = [UIImage imageWithCGImage:imageMasked];

    CGImageRelease(imageMasked);

    // 创建一个bitmap的context

    // 并把它设置成为当前正在使用的context

    UIGraphicsBeginImageContext(CGSizeMake(winSize.width*0.6, winSize.height*0.6));

    

    // 绘制改变大小的图片

    [newImage drawInRect:CGRectMake(0, 0, winSize.width*0.6, winSize.height*0.6)];

    

    // 从当前context中创建一个改变大小后的图片

    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

    

    // 使当前的context出堆栈

    UIGraphicsEndImageContext();

 }

 

最终的newImage就是你最终希望得到的图片。