相关图像处理以及UIGraphicsBeginImageContext系列知识

UIGraphicsBeginImageContext创建了一个基于位图的上下文，并将其设置为当前上下文（context）.

Void UIGraphicsBeginImageContext（CGSize size）;

Void UIGraphicsBeginImageContextWithOptions(CGSizesize, BOOL opaque, CGFloat scale); //opaque透明开关，如果图形完全不用透明，设置YES优化位图存储；scale缩放因子

UIImage处理

1， 等比缩放

-（UIImage *）scaleImage:(UIImage *)image toScale:(float)scaleSize{

UIGraphicsBeginImageContext(CGSizeMake(image.size.width*scaleSize, image.size.height * scaleSize); //scaleSize为缩放比例, 创建基于位图的图形上下文

[image drawInRect:CGRectMake(0, 0, image.size.width*scaleSize, image.size.height *scaleSize )];//绘图

UIImage *scaledImage =UIGraphicsGetImageFromCurrentImageContext();

//获得图片

UIGraphicsEndImageContext();

//从当前堆栈中删除quartz2D绘图环境

return scaledImage; //返回缩放后的图片

}

2， 自定义大小

-（UIImage *）reSizeImage:(UIImage *)image toSize:(CGSize)resize {

//创建基于位图的图形上下文

IGraphicsBeginImageContext(CGSizeMake(resize.width, resize.height));

[image drawInRect:CGRectMake(0, , 0, resize.width, reSize.height)];

UIImage *reSizeImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();//从当前堆栈中删除quartz2D绘图环境

return reSizeImage

}

3， 存储图片

3.1存储到app文件中

NSString *path =[[NSHomeDirectory()stringByAppendingPathComponent:@”Documents”] stringByAppendingPathComponent:@”image.png];

[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];

3.2存储到手机的图片库中

CGImageRef screen =UIGetScreenImage(); //截取整个Screen

UIImage *image = [UIImage imageWithCGImage:screen];

CGImageRelease(screen);

UIImageWriteToSavedPhotosAlbum(image, self, nil, nil); //写到手机图片库

4， 对于特定UIView的截屏

-（UIImage *）captureView:(UIView *)theView

{

CGRect rect = theView.frame;

UIGraphicsBeginImageContext(rect.size);

CGContextRef context = UIGraphicsGetCurrentContext();

[theView.layer renderInContext:context];

UIImage *img= [UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return img;

}

5， 截取指定区域

//方法一： 使用的200*200的图片，截取的是左上角

-(UIImage *)getImageFromImage{

//大图bigImage

//定义myImageRect，截图的区域

CGRect myImageRect = CGRectMake(0, 0, 100, 100);

UIImage* bigImage= [UIImage imageNamed:@"1.jpg"];

CGImageRef imageRef = bigImage.CGImage;

CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef,myImageRect);

CGSize size;

size.width = 100.0;

size.height = 100.0;

UIGraphicsBeginImageContext(size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextDrawImage(context, myImageRect, subImageRef);

UIImage* smallImage = [UIImageimageWithCGImage:subImageRef];

UIGraphicsEndImageContext();

return smallImage;

}

//方法二

UIImage *image=[UIImage imageNamed:@"1.jpg"];

CGRect rect = CGRectMake(0, 0, 100, 100);//创建矩形框

UIImageView *contentView = [[UIImageView alloc] initWithFrame:rect];

contentView.image=[UIImage imageWithCGImage:CGImageCreateWithImageInRect([imageCGImage], rect)];

6， 合并两张图片

- (UIImage*)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {

UIGraphicsBeginImageContext(image1.size);

// Draw image1

[image1 drawInRect:CGRectMake(0, 0, image1.size.width,image1.size.height)];

// Draw image2

[image2 drawInRect:CGRectMake(0, 0, image2.size.width,image2.size.height)];

UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return resultingImage;

}