Resize image and keep aspect ratio

 -(UIImage *)resizeImage:(UIImage *)image {


   int w = image.size.width;   
   int h = image.size.height; 
   CGImageRef imageRef = [image CGImage]; 
   int width, height; 
   int destWidth = 640;
   int destHeight = 480; 
if(w > h){
        width = destWidth;  height = h*destWidth/w; 
   }
else
    {
     height = destHeight;
     width = w*destHeight/h;
        } 
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
  CGContextRef bitmap;  bitmap = CGBitmapContextCreate(NULL, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedFirst);


if (image.imageOrientation == UIImageOrientationLeft)
   {
       CGContextRotateCTM (bitmap, M_PI/2); 
       CGContextTranslateCTM (bitmap, 0, -height);
      }
 else if (image.imageOrientation == UIImageOrientationRight) { 

      CGContextRotateCTM (bitmap, -M_PI/2);
     CGContextTranslateCTM (bitmap, -width, 0);
   }
else if (image.imageOrientation == UIImageOrientationUp) {


}
  else if (image.imageOrientation == UIImageOrientationDown) {

     CGContextTranslateCTM (bitmap, width,height);
    CGContextRotateCTM (bitmap, -M_PI); 
  }
    CGContextDrawImage(bitmap, CGRectMake(0, 0, width, height), imageRef); 
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
     UIImage *result = [UIImage imageWithCGImage:ref];
    CGContextRelease(bitmap);  CGImageRelease(ref);  return result;
}