每日分享 － 图像压缩成指定大小（高度/宽度）

 

复制代码

    #import <Foundation/Foundation.h>
    @interface UIImage (UIImageExt)
    - (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize;
    @end




复制代码

    #import "UIImageExt.h"
    @implementation UIImage (UIImageExt)
    - (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize
    {
        UIImage *sourceImage = self;
        UIImage *newImage = nil;      
        CGSize imageSize = sourceImage.size;
        CGFloat width = imageSize.width;
        CGFloat height = imageSize.height;
        CGFloat targetWidth = targetSize.width;
        CGFloat targetHeight = targetSize.height;
        CGFloat scaleFactor = 0.0;
        CGFloat scaledWidth = targetWidth;
        CGFloat scaledHeight = targetHeight;
        CGPoint thumbnailPoint = CGPointMake(0.0,0.0);
        
        if (CGSizeEqualToSize(imageSize, targetSize) == NO)
        {
            CGFloat widthFactor = targetWidth / width;
            CGFloat heightFactor = targetHeight / height;
            
            if (widthFactor > heightFactor)
                scaleFactor = widthFactor; // scale to fit height
            else
                scaleFactor = heightFactor; // scale to fit width
            scaledWidth  = width * scaleFactor;
            scaledHeight = height * scaleFactor;
            
            // center the image
            if (widthFactor > heightFactor)
            {
                thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
            }
            else
                if (widthFactor < heightFactor)
                {
                    thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
                }
        }      
        
        UIGraphicsBeginImageContext(targetSize); // this will crop
        
        CGRect thumbnailRect = CGRectZero;
        thumbnailRect.origin = thumbnailPoint;
        thumbnailRect.size.width  = scaledWidth;
        thumbnailRect.size.height = scaledHeight;
        
        [sourceImage drawInRect:thumbnailRect];
        
        newImage = UIGraphicsGetImageFromCurrentImageContext();
        if(newImage == nil)
            NSLog(@"could not scale image");
        
        //pop the context to get back to the default
        UIGraphicsEndImageContext();
        return newImage;
    }
    @end

 

裁剪图片和等比列缩放图片

@interface UIImage(UIImageScale)  
-(UIImage*)getSubImage:(CGRect)rect;  
-(UIImage*)scaleToSize:(CGSize)size;  
@end  
   
@implementation UIImage(UIImageScale)  
   
//截取部分图像  
-(UIImage*)getSubImage:(CGRect)rect  
{  
    CGImageRef subImageRef = CGImageCreateWithImageInRect(self.CGImage, rect);  
    CGRect smallBounds = CGRectMake(0, 0, CGImageGetWidth(subImageRef), CGImageGetHeight(subImageRef));  
      
    UIGraphicsBeginImageContext(smallBounds.size);  
    CGContextRef context = UIGraphicsGetCurrentContext();  
    CGContextDrawImage(context, smallBounds, subImageRef);  
    UIImage* smallImage = [UIImage imageWithCGImage:subImageRef];  
    UIGraphicsEndImageContext();  
      
    return smallImage;  
}  
   
//等比例缩放  
-(UIImage*)scaleToSize:(CGSize)size   
{  
    CGFloat width = CGImageGetWidth(self.CGImage);  
    CGFloat height = CGImageGetHeight(self.CGImage);  
      
    float verticalRadio = size.height*1.0/height;   
    float horizontalRadio = size.width*1.0/width;  
      
    float radio = 1;  
    if(verticalRadio>1 && horizontalRadio>1)  
    {  
        radio = verticalRadio > horizontalRadio ? horizontalRadio : verticalRadio;     
    }  
    else  
    {  
        radio = verticalRadio < horizontalRadio ? verticalRadio : horizontalRadio;     
    }  
      
    width = width*radio;  
    height = height*radio;  
      
    int xPos = (size.width - width)/2;  
    int yPos = (size.height-height)/2;  
      
    // 创建一个bitmap的context    
    // 并把它设置成为当前正在使用的context    
    UIGraphicsBeginImageContext(size);    
      
    // 绘制改变大小的图片    
    [self drawInRect:CGRectMake(xPos, yPos, width, height)];    
      
    // 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();    
      
    // 返回新的改变大小后的图片    
    return scaledImage;  
}  
@end  


然后在下面方法里面调用就可以了！ 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{ 
    // Override point for customization after application launch. 
    UIImage *image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://img21.mtime.cn/mg/2011/09/24/112524.53149978.jpg"]] ]; 
    
    
    // 裁剪图片 
    //image = [image getSubImage:CGRectMake(10, 10, 70, 80)]; 
    
    //等比列缩放 
    
    image = [image scaleToSize:CGSizeMake(200, 300)]; 
    
    UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; 
    
    [self.window addSubview:imageView]; 
    
    NSLog(@"image.size:%@",NSStringFromCGSize(CGSizeMake(imageView.image.size.width, imageView.image.size.height)));   //打印获取的网络图片的宽度和高度 
    
    [self.window makeKeyAndVisible]; 
    return YES; 
} 


//--------------截取部分图片到指定位置------------------------- 

图片(UIImage*) img 
要截取的起始坐标sx:(int) sx1 sy:(int)sy1 
要截取的长度和宽度sw:(int) sw1 sh:(int) sh1 
最终要显示的坐标desx:(int) desx1 desy:(int)desy1 

-(UIImage*)objectiveDrawRegion:(UIImage*) img sx:(int) sx1 sy:(int)sy1 sw:(int) sw1 sh:(int) sh1 desx:(int) desx1 desy:(int)desy1{ 
[self saveImage:img name:@"objectiveDrawRegion1.png"]; 

//创建图片缓冲 
void *imageDataRegion=malloc(screenWidth*screenHeight*32); 
CGColorSpaceRef iColorSpaceRegion=CGColorSpaceCreateDeviceRGB(); 
    CGContextRefiDeviceRegion=CGBitmapContextCreate(imageDataRegion,screenWidth,screenHeight,8,4*screenWidth,iColorSpaceRegion,kCGImageAlphaPremultipliedLast);



//剪切区域 
    CGRect clipRegion=CGRectMake(sx1,sy1,sw1,sh1); 
    CGContextClipToRect(iDeviceRegion, clipRegion); 
    
    CGFloat widthf=img.size.width; 
    CGFloat heightf=img.size.height; 

CGRect  cg=CGRectMake(0.0, 0.0, widthf, heightf); 
//画底图 
    CGContextDrawImage(iDeviceRegion,cg, img.CGImage); 

//将缓冲形成图片 
    CGImageRef ioffRegion=CGBitmapContextCreateImage(iDeviceRegion); 
  
CGRect  cg1=CGRectMake(desx1, desy1, sw1, sh1); 
UIImage *ui=[UIImage imageWithCGImage:ioffRegion]; 

CGContextDrawImage(当前context,cg1, ui.CGImage); 


//清除缓冲 
   CGColorSpaceRelease(iColorSpaceRegion); 
   CGContextRelease(iDeviceRegion); 
   CGImageRelease(ioffRegion); 
   free(imageDataRegion); 
//    iDeviceRegion=NULL; 
//    imageDataRegion=0; 

return ui; 
}