iOS自带的提供了一个API如下
NSData *UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality);
在Iphone上有两种读取图片数据的简单方法: UIImageJPEGRepresentation和UIImagePNGRepresentation. UIImageJPEGRepresentation函数需要两个参数:图片的引用和压缩系数.而UIImagePNGRepresentation只需要图片引用作为参数.通过在实际使用过程中,比较发现: UIImagePNGRepresentation(UIImage* image) 要比UIImageJPEGRepresentation(UIImage* image, 1.0) 返回的图片数据量大很多.譬如,同样是读取摄像头拍摄的同样景色的照片, UIImagePNGRepresentation()返回的数据量大小为199K ,而 UIImageJPEGRepresentation(UIImage* image, 1.0)返回的数据量大小只为140KB,比前者少了50多KB.如果对图片的清晰度要求不高,还可以通过设置 UIImageJPEGRepresentation函数的第二个参数,大幅度降低图片数据量.譬如,刚才拍摄的图片, 通过调用UIImageJPEGRepresentation(UIImage* image, 1.0)读取数据时,返回的数据大小为140KB,但更改压缩系数后,通过调用UIImageJPEGRepresentation(UIImage* image, 0.5)读取数据时,返回的数据大小只有11KB多,大大压缩了图片的数据量 ,而且从视角角度看,图片的质量并没有明显的降低.因此,在读取图片数据内容时,建议优先使用UIImageJPEGRepresentation,并可根据自己的实际使用场景,设置压缩系数,进一步降低图片数据量大小。
UIImage *imageNew = [info objectForKey:@"UIImagePickerControllerOriginalImage"];imageNew = [self imageWithImage:imageNew scaledToSize:CGSizeMake(100, 100)];NSData *imageData = UIImageJPEGRepresentation(imageNew, 0.0001);m_selectImage = [UIImage imageWithData:imageData];
.h具体code
#import <Foundation/Foundation.h>@interface UIImage (UIImageExt)- (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size;- (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize;@end.m具体code#import "UIImageExt.h"@implementation UIImage (UIImageExt)- (UIImage *)scaleToSize:(UIImage *)img size:(CGSize)size{// 创建一个bitmap的context// 并把它设置成为当前正在使用的contextUIGraphicsBeginImageContext(size);// 绘制改变大小的图片[img drawInRect:CGRectMake(0, 0, size.width, size.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;}- (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 heightelsescaleFactor = heightFactor; // scale to fit widthscaledWidth = width * scaleFactor;scaledHeight = height * scaleFactor;// center the imageif (widthFactor > heightFactor){thumbnailPoint.y = (targetHeight – scaledHeight) * 0.5;}elseif (widthFactor < heightFactor){thumbnailPoint.x = (targetWidth – scaledWidth) * 0.5;}}UIGraphicsBeginImageContext(targetSize); // this will cropCGRect 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 defaultUIGraphicsEndImageContext();return newImage;}@end
，最可怕的敌人，就是没有坚强的信念。
