调整UIImage和imagePickerController内存压力？

Question

应用程序崩溃考虑使用imagePickerController 在这里，我想从imagepickercontroller旋转图像照片后

- (void)imagePickerController:(UIImagePickerController *)picker1 didFinishPickingMediaWithInfo:(NSDictionary *)info 
{ 
UIImage *chosenImage = info[UIImagePickerControllerOriginalImage]; 
if (chosenImage.imageOrientation!= UIImageOrientationUp) { 
    UIGraphicsBeginImageContextWithOptions(self.view.bounds.size,self.view.opaque,0.0); 
     [chosenImage drawInRect:(CGRect){0, 0,chosenImage.size}]; 
    chosenImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

} 
UIImage *imageToDisplay =chosenImage; 
} 

它提供了10-MB image.How以KB压缩它在非常低的尺寸的图像？

Answer 1

只要使用这样的东西。

NSURL *url = info[UIImagePickerControllerReferenceURL]; 

ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset) { 
    ALAssetRepresentation *rep = [myasset defaultRepresentation]; 
    CGImageRef imageRef = [rep fullResolutionImage]; 
    if (imageRef) { 
// here is your image 
     chosenImage = [UIImage imageWithCGImage:iref]; 
    } 
}; 

ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *error) 
{ 
     NSLog(@"Error -> %@",[error localizedDescription]); 
}; 

ALAssetsLibrary* assetslibrary = [[[ALAssetsLibrary alloc] init] autorelease]; 
     [assetslibrary assetForURL:url 
         resultBlock:resultblock 
         failureBlock:failureblock]; 

或者你可以使用这样的代码

CGSize newSize = CGSizeMake(1000.0f, 1000.0f); 
UIGraphicsBeginImageContext(newSize); 
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; 
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

这会给你1000 * 1000像素的图片。

Answer 2

我已经找到了解决方案，以压缩图像

//Put this code in didfinish UIimagepickercontroller 
UIImage *chosenImage = info[UIImagePickerControllerOriginalImage]; 
NSData *imgData= UIImageJPEGRepresentation(chosenImage,0.1);//0.1 is loosy compression 
UIImage *compressedImage=[UIImage imageWithData:imgData]; 
UIImage *resizedImage=[self imageWithImage:compressedImage scaledToSize:CGSizeMake(290, 390)]; 

下面的代码是调整图像

-(UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize { 
//UIGraphicsBeginImageContext(newSize); 
// In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution). 
// Pass 1.0 to force exact pixel size. 
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0); 
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; 
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 
return newImage; 
}