whatsapp-image-compression

#define MAXIMUM_IMAGE_WEIGHT 1024*1024

- (UIImage *)compressImage:(UIImage *)image {
    float actualHeight = image.size.height;
    float actualWidth = image.size.width;
    float maxHeight = 600.0;
    float maxWidth = 800.0;
    float imgRatio = actualWidth/actualHeight;
    float maxRatio = maxWidth/maxHeight;
    
    float compressionQuality = 0.8;//80 percent compression
    
    if (actualHeight > maxHeight || actualWidth > maxWidth) {
        if(imgRatio < maxRatio){
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight;
            actualWidth = imgRatio * actualWidth;
            actualHeight = maxHeight;
        }
        else if(imgRatio > maxRatio){
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth;
            actualHeight = imgRatio * actualHeight;
            actualWidth = maxWidth;
        }else{
            actualHeight = maxHeight;
            actualWidth = maxWidth;
        }
    }
    
    CGRect rect = CGRectMake(0.0, 0.0, actualWidth, actualHeight);
    UIGraphicsBeginImageContext(rect.size);
    [image drawInRect:rect];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

    NSData *imageData = UIImageJPEGRepresentation(img, compressionQuality);
    
    // iteratively lowers compression quality to obtain an acceptable image weight.
    while (imageData.length >= MAXIMUM_IMAGE_WEIGHT && compressionQuality > 0)
    {
        compressionQuality -= 0.05; 
        imageData = UIImageJPEGRepresentation(img, compressionQuality);
    }

    UIGraphicsEndImageContext();

    return [UIImage imageWithData:imageData];
}

I needed to replace line 32 with the following iterative compression to limit the image weight with the MAXIMUM_IMAGE_WEIGHT constant.
Hence I'll have two factor limit : size (pixels) and weight (kilobytes).