问ALAsset图像大小

EN

float width = asset.defaultRepresentation.dimensions.width;
float height = asset.defaultRepresentation.dimensions.height;

// This method requires the ImageIO.framework
// This requires memory for the size of the image in bytes, but does not decompress it.
- (CGSize)sizeOfImageWithData:(NSData*) data;
{
    CGSize imageSize = CGSizeZero;
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef) data, NULL);
    if (source)
    {
        NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] forKey:(NSString *)kCGImageSourceShouldCache];

        NSDictionary *properties = (__bridge_transfer NSDictionary*) CGImageSourceCopyPropertiesAtIndex(source, 0, (__bridge CFDictionaryRef) options);

        if (properties)
        {
            NSNumber *width = [properties objectForKey:(NSString *)kCGImagePropertyPixelWidth];
            NSNumber *height = [properties objectForKey:(NSString *)kCGImagePropertyPixelHeight];
            if ((width != nil) && (height != nil))
                imageSize = CGSizeMake(width.floatValue, height.floatValue);
        }
        CFRelease(source);
    }
    return imageSize;
}

- (CGSize)sizeOfAssetRepresentation:(ALAssetRepresentation*) assetRepresentation;
{
    // It may be more efficient to read the [[[assetRepresentation] metadata] objectForKey:@"PixelWidth"] integerValue] and corresponding height instead.
    // Read all the bytes for the image into NSData.
    long long imageDataSize = [assetRepresentation size];
    uint8_t* imageDataBytes = malloc(imageDataSize);
    [assetRepresentation getBytes:imageDataBytes fromOffset:0 length:imageDataSize error:nil];
    NSData *data = [NSData dataWithBytesNoCopy:imageDataBytes length:imageDataSize freeWhenDone:YES];

    return [self sizeOfImageWithData:data];
}

- (CGSize)sizeOfAsset:(ALAsset*) asset;
{
    return [self sizeOfAssetRepresentation:[asset defaultRepresentation]];
}