Question

我希望在将图像存储为NSData对象之前压缩图像。

下面是代码，它可以帮助我获取图像的NSData对象。

NSURL *referenceURL = [info objectForKey:UIImagePickerControllerReferenceURL];
        ALAssetsLibrary *library1 = [[ALAssetsLibrary alloc] init];
        [library1 assetForURL:referenceURL resultBlock:^(ALAsset *asset)
         {

             int byteArraySize = asset.defaultRepresentation.size;

             NSMutableData* rawData = [[NSMutableData alloc]initWithCapacity:byteArraySize];
             void* bufferPointer = [rawData mutableBytes];

             NSError* error=nil;
             [asset.defaultRepresentation getBytes:bufferPointer fromOffset:0 length:byteArraySize error:&error];
             if (error) {
                 NSLog(@"%@",error);
             }
             rawData = [NSMutableData dataWithBytes:bufferPointer length:byteArraySize];
}

任何帮助将不胜感激。

Answer 1

UIImagePickerController会返回压缩图像，但您也可以使用此内置的UIKit函数和PNG的相关函数来控制格式和压缩：

NSData* UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality);

如果referenceURL返回一个字符串，您可能需要创建一个NSURL。

NSImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL: referenceURL]];
NSData *compressedImage = UIImageJPEGRepresentation(image, .1); //.1 is low quality

Answer 2

如果您正在使用UIImagePickerController，则返回的图像将是JPEG，已经压缩（我认为）。如果没有，您可以使用AVAssetWriter将图像写为JPEG或PNG。

Answer 3

简单易用： -

    -(UIImage *)fireYourImageForCompression:(UIImage *)imgComing{
NSData *dataImgBefore   = [[NSData alloc] initWithData:UIImageJPEGRepresentation((imgComing), 1.0)];//.1 BEFORE COMPRESSION
int imageSizeBefore     = (int)dataImgBefore.length;


NSLog(@"SIZE OF IMAGE: %i ", imageSizeBefore);
NSLog(@"SIZE OF IMAGE in Kb: %i ", imageSizeBefore/1024);



NSData *dataCompressedImage = UIImageJPEGRepresentation(imgComing, .1); //.1 is low quality
int sizeCompressedImage     = (int)dataCompressedImage.length;
NSLog(@"SIZE AFTER COMPRESSION  OF IMAGE: %i ", sizeCompressedImage);
NSLog(@"SIZE AFTER COMPRESSION OF IMAGE in Kb: %i ", sizeCompressedImage/1024); //AFTER

//now change your image from compressed data
imgComing = [UIImage imageWithData:dataCompressedImage];


return imgComing;}

从NSData以编程方式压缩Iphone中的图像

3 个答案: