//限制圖片的大小為：1M
#define maxImageSize 1024.0

//限制圖片大小，傳入的maxSize單位是KB
+ (NSData *)reSizeImageData:(UIImage *)sourceImage maxSizeWithKB:(CGFloat)maxSize
{
    if (!sourceImage) {
        return nil;
    }
    NSData *imageData = UIImageJPEGRepresentation(sourceImage, 1.0);
    CGFloat sizeOriginKB = imageData.length / 1024.0;
    
    CGFloat resizeRate = 0.9;
    while (sizeOriginKB > maxSize && resizeRate > 0.1) {
        imageData = UIImageJPEGRepresentation(sourceImage, resizeRate);
        sizeOriginKB = imageData.length / 1024.0;
        resizeRate -= 0.1;
    }
    
    return imageData;
}