ios中映像進行壓縮方法匯總

 　　在Iphone上有兩種讀取圖片資料的簡單方法: UIImageJPEGRepresentation和UIImagePNGRepresentation. UIImageJPEGRepresentation函數需要兩個參數:圖片的引用和壓縮係數.而UIImagePNGRepresentation只需要圖片引用作為參數.

　　方法一：

　　代碼如下:

　　- (UIImage*)scaleFromImage:(UIImage*)image scaledToSize:(CGSize)newSize

　　{

　　CGSize imageSize = image.size;

　　CGFloat width = imageSize.width;

　　CGFloat height = imageSize.height;

　　if (width <= newSize.width && height <= newSize.height){

　　return image;

　　}

　　if (width == 0 || height == 0){

　　return image;

　　}

　　CGFloat widthFactor = newSize.width / width;

　　CGFloat heightFactor = newSize.height / height;

　　CGFloat scaleFactor = (widthFactor

　　CGFloat scaledWidth = width * scaleFactor;

　　CGFloat scaledHeight = height * scaleFactor;

　　CGSize targetSize = CGSizeMake(scaledWidth,scaledHeight);

　　UIGraphicsBeginImageContext(targetSize);

　　[image drawInRect:CGRectMake(0,0,scaledWidth,scaledHeight)];

　　UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

　　UIGraphicsEndImageContext();

　　return newImage;

　　}

　　方法二：

　　.h具體code

　　 代碼如下:

　　#import

　　@interface UIImage (UIImageExt)

　　- (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size;

　　- (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize;

　　@end

　　.m具體code

　　 代碼如下:

　　#import "UIImageExt.h"

　　@implementation UIImage (UIImageExt)

　　- (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size{

　　// 建立一個bitmap的context

　　// 並把它設定成為當前正在使用的context

　　UIGraphicsBeginImageContext(size);

　　// 繪製改變大小的圖片

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

　　// 從當前context中建立一個改變大小後的圖片

　　UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();

　　// 使當前的context出堆棧

　　UIGraphicsEndImageContext();

　　// 返回新的改變大小後的圖片

　　return scaledImage;

　　}

　　- (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

　　方法三：(本人項目中使用的方法)

　　 代碼如下:

　　-(UIImage *) imageCompressForWidth:(UIImage *)sourceImage targetWidth:(CGFloat)defineWidth

　　{

　　CGSize imageSize = sourceImage.size;

　　CGFloat width = imageSize.width;

　　CGFloat height = imageSize.height;

　　CGFloat targetWidth = defineWidth;

　　CGFloat targetHeight = (targetWidth / width) * height;

　　UIGraphicsBeginImageContext(CGSizeMake(targetWidth, targetHeight));

　　[sourceImage drawInRect:CGRectMake(0,0,targetWidth, targetHeight)];

　　UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

　　UIGraphicsEndImageContext();

　　return newImage;

　　}

　　以上所述就是本文的全部內容了，希望大家能夠喜歡。