图片压缩处理

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#import <UIKit/UIKit.h>

@interface UIImageTransformation : UIImage{

}

+ (UIImage*)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize;

+ (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize image:(UIImage*)image;

#pragma mark - image scale utility

+ (UIImage *)imageByScalingToMaxSize:(UIImage *)sourceImage;

+ (UIImage *)imageByScalingAndCroppingForSourceImage:(UIImage *)sourceImage targetSize:(CGSize)targetSize;

@end

#import "UIImageTransformation.h"

#import "DeviceManage.h"

@implementation UIImageTransformation

-(id)init{

self = [super init];

return self;

}

+ (UIImage*)imageByScalingAndCroppingForSize:(CGSize)targetSize image:(UIImage*)image

{

// DLog(@"the image width is :%f", image.size.width);

// DLog(@"the image height is :%f", image.size.height);

//UIImage 压缩后的图片

UIImage *newImage = nil;

//原图片大小

CGSize imageSize = image.size;

//原图片宽度

CGFloat width = imageSize.width;

//原图片高度

CGFloat height = imageSize.height;

//欲压缩宽度

CGFloat targetWidth = targetSize.width;

//欲压缩高度

CGFloat targetHeight = targetSize.height;

//压缩比例系数（初始化为0）

CGFloat scaleFactor = 0.0;

//图片的宽度和高度小于欲压缩的宽度和高度，不需要压缩

if (width <= targetWidth && height <= targetHeight) {

return image;

}

//图片的宽度和高度都等于0，不需要压缩

if (width == 0 || height == 0) {

return image;

}

//宽度比例

CGFloat scaledWidth = targetWidth;

//高度比例

CGFloat scaledHeight = targetHeight;

//压缩点

CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

如果原图片大小跟欲压缩大小相同，则不执行压缩动作，否则执行压缩动作

执行：

if ((CGSizeEqualToSize(imageSize, targetSize) == NO)&&(imageSize.width!=0)&&(imageSize.height!=0))

{

//宽度系数，格式 50／100＝0.5

CGFloat widthFactor = targetWidth / width;

//高度系数格式 50／100＝0.5

CGFloat heightFactor = targetHeight / height;

if (widthFactor > heightFactor)

scaleFactor = widthFactor; // scale to fit height

else

scaleFactor = heightFactor; // scale to fit width

//压缩后的宽度＝原宽度＊宽度压缩系数

scaledWidth = width * scaleFactor;

//压缩后的宽度＝原高度＊高度压缩系数

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;

}

//以下执行压缩动作

UIGraphicsBeginImageContext(targetSize); // this will crop

CGRect thumbnailRect = CGRectZero;

thumbnailRect.origin = thumbnailPoint;

thumbnailRect.size.width = scaledWidth;

thumbnailRect.size.height = scaledHeight;

[image drawInRect:thumbnailRect];

newImage = UIGraphicsGetImageFromCurrentImageContext();

DLog(@"new width is :%f", newImage.size.width);

DLog(@"new height is :%f", newImage.size.height);

if(newImage == nil)

//pop the context to get back to the default

UIGraphicsEndImageContext();

return newImage;

}

#pragma mark - image scale utility

+ (UIImage *)imageByScalingToMaxSize:(UIImage *)sourceImage {

// if (sourceImage.size.width/2 < ScreenWidth)

// return sourceImage;

CGFloat btWidth = 0.0f;

CGFloat btHeight = 0.0f;

CGFloat screenWidth = [[DeviceManage deviceManage] screenWidth];

if (sourceImage.size.height/2 < screenWidth) {

btHeight = screenWidth*2;

btWidth = sourceImage.size.width * (screenWidth*2/sourceImage.size.height);

// btWidth = sourceImage.size.width * (ScreenWidth*2 / sourceImage.size.width);

CGSize targetSize = CGSizeMake(btWidth, btHeight);

return [self imageByScalingAndCroppingForSourceImage:sourceImage targetSize:targetSize];

}

if (sourceImage.size.width > sourceImage.size.height) {

btHeight = screenWidth*2;

btWidth = sourceImage.size.width * (screenWidth*2 / sourceImage.size.height);

} else {

btWidth = screenWidth*2 ;

btHeight = sourceImage.size.height * (screenWidth*2 / sourceImage.size.width);

}

CGSize targetSize = CGSizeMake(btWidth, btHeight);

return [self imageByScalingAndCroppingForSourceImage:sourceImage targetSize:targetSize];

}

+ (UIImage *)imageByScalingAndCroppingForSourceImage:(UIImage *)sourceImage targetSize:(CGSize)targetSize {

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;

}

//压缩图片

+ (UIImage*)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize

{

// Create a graphics image context

UIGraphicsBeginImageContext(newSize);

// Tell the old image to draw in this new context, with the desired

// new size

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

// Get the new image from the context

UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

// End the context

UIGraphicsEndImageContext();

// Return the new image.

return newImage;

}

@end

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