一.读取图片
1.从资源(resource)读取
- UIImage* image=[UIImage imageNamed:@"1.jpg"];
2.从网络读取
- NSURL *url=[NSURL URLWithString:@"http://attach.bbs.miui.com/forum/201203/20/170226n5qcwdpusnjdsswy.jpg"];
- UIImage *imgFromUrl =[[UIImage alloc]initWithData:[NSData dataWithContentsOfURL:url]];
3.从手机本地读取
- //读取本地图片非resource
- NSString *aPath3=[NSString stringWithFormat:@"%@/Documents/%@.jpg",NSHomeDirectory(),@"test"];
- UIImage *imgFromUrl3=[[UIImage alloc]initWithContentsOfFile:aPath3];
- UIImageView* imageView3=[[UIImageView alloc]initWithImage:imgFromUrl3];
- //add ImageIO.framework and #import
- CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url, NULL);
- CGImageRef img= CGImageSourceCreateImageAtIndex(source,0,NULL);
- CGContextRef ctx=UIGraphicsGetCurrentContext();
- CGContextSaveGState(ctx);
- //transformCTM的2种方式
- //CGContextConcatCTM(ctx, CGAffineTransformMakeScale(.2, -0.2));
- //CGContextScaleCTM(ctx,1,-1);
- //注意坐标要反下,用ctx来作为图片源
- CGImageRef capture=CGBitmapContextCreateImage(ctx);
- CGContextDrawImage(ctx, CGRectMake(160, 0, 160, 230), [image CGImage]);
- CGContextDrawImage(ctx, CGRectMake(160, 230, 160, 230), img);
- CGImageRef capture2=CGBitmapContextCreateImage(ctx);
5.用Quartz的CGImageSourceRef来读取图片
- CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url, NULL);
- CGImageRef img= CGImageSourceCreateImageAtIndex(source,0,NULL);
二.保存图片
1.转换成NSData来保存图片(imgFromUrl是UIImage)
- //保存图片 2种获取路径都可以
- //NSArray*paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
- //NSString*documentsDirectory=[paths objectAtIndex:0];
- //NSString*aPath=[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.jpg",@"test"]];
- NSString *aPath=[NSString stringWithFormat:@"%@/Documents/%@.jpg",NSHomeDirectory(),@"test"];
- NSData *imgData = UIImageJPEGRepresentation(imgFromUrl,0);
- [imgData writeToFile:aPath atomically:YES];
2.用Quartz的CGImageDestinationRef来输出图片,这个方式不常见,所以不做介绍,详细可以看apple文档Quartz 2D Programming Guide
三.绘制图(draw|painting)
1.UIImageView方式加入到UIView层
- UIImageView* imageView=[[UIImageView alloc]initWithImage:image];
- imageView.frame=CGRectMake(0, 0, 320, 480);
- [self addSubview:imageView];
- [imageView release];
- [image4 drawAtPoint:CGPointMake(100, 0)];
- CGContextDrawImage(ctx, CGRectMake(160, 0, 160, 230), [image CGImage]);
4.CGLayer
这个是apple推荐的一种offscreen的绘制方法,相比bitmapContext更好,因为它似乎会利用iphone硬件(drawing-card)加速
- CGLayerRef cg=CGLayerCreateWithContext(ctx, CGSizeMake(320, 480), NULL);
- //需要将CGLayerContext来作为缓存context,这个是必须的
- CGContextRef layerContext=CGLayerGetContext(cg);
- CGContextDrawImage(layerContext, CGRectMake(160, 230, 160, 230), img);
- CGContextDrawLayerAtPoint(ctx, CGPointMake(0, 0), cg);
5.CALayer的contents
- UIImage* image=[UIImage imageNamed:@"1.jpg"];
- CALayer *ly=[CALayer layer];
- ly.frame=CGRectMake(0, 0, 320, 460);
- ly.contents=[image CGImage];
- [self.layer addSublayer:ly];
四.其它
1.CGImage和UIImage互换
这样就可以随时切换UIKit和Quartz之间类型,并且选择您熟悉的方式来处理图片.
CGImage cgImage=[uiImage CGImage];
UIImage* uiImage=[UIImage imageWithCGImage:cgImage];