获取UIImage的大小(字节长度)而不是高度和宽度

Question

我想要得到一个长度UIImage.不是图像的宽度或高度,而是数据的大小.

Answer 1

 UIImage *img = [UIImage imageNamed:@"sample.png"];
 NSData *imgData = UIImageJPEGRepresentation(img, 1.0); 
 NSLog(@"Size of Image(bytes):%d",[imgData length]);

Answer 2

a的基础数据UIImage可以变化,因此对于相同的"图像",可以具有不同大小的数据.你可以做的一件事是使用UIImagePNGRepresentation或UIImageJPEGRepresentation得到两者的等效NSData结构,然后检查它的大小.

Answer 3

使用UIImage的CGImage属性.然后使用CGImageGetBytesPerRow*
CGImageGetHeight 的组合,添加sizeof UIImage,你应该在实际大小的几个字节内.

这将返回未压缩的图像大小,如果你想将它用于malloc以便为位图操作做准备(假设RGB字节格式为3字节,Alpha格式为1字节):

int height = image.size.height,
    width = image.size.width;
int bytesPerRow = 4*width;
if (bytesPerRow % 16)
    bytesPerRow = ((bytesPerRow / 16) + 1) * 16;
int dataSize = height*bytesPerRow;

Answer 4

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)editInfo
{
   UIImage *image=[editInfo valueForKey:UIImagePickerControllerOriginalImage];
   NSURL *imageURL=[editInfo valueForKey:UIImagePickerControllerReferenceURL];
   __block long long realSize;

   ALAssetsLibraryAssetForURLResultBlock resultBlock=^(ALAsset *asset)
   {
      ALAssetRepresentation *representation=[asset defaultRepresentation];
      realSize=[representation size];
   };

   ALAssetsLibraryAccessFailureBlock failureBlock=^(NSError *error)
   {
      NSLog(@"%@", [error localizedDescription]);
   };

   if(imageURL)
   {
      ALAssetsLibrary *assetsLibrary=[[[ALAssetsLibrary alloc] init] autorelease];
      [assetsLibrary assetForURL:imageURL resultBlock:resultBlock failureBlock:failureBlock];
   }
}

Answer 5

Swift中的示例:

let img: UIImage? = UIImage(named: "yolo.png")
let imgData: NSData = UIImageJPEGRepresentation(img, 0)
println("Size of Image: \(imgData.length) bytes")

Answer 6

以下是获得答案的最快、最干净、最通用且最不容易出错的方法。在一个类别中UIImage+MemorySize：

#import <objc/runtime.h>

- (size_t) memorySize
{
  CGImageRef image = self.CGImage;
  size_t instanceSize = class_getInstanceSize(self.class);
  size_t pixmapSize = CGImageGetHeight(image) * CGImageGetBytesPerRow(image);
  size_t totalSize = instanceSize + pixmapSize;
  return totalSize;
}

或者，如果您只想要实际的位图而不是 UIImage 实例容器，那么它确实如此简单：

- (size_t) memorySize
{
  return CGImageGetHeight(self.CGImage) * CGImageGetBytesPerRow(self.CGImage);
}