Image Resize in C# - Algorith to determine resize dimensions (height and width)

Question

I need to scale down an image that has a height or width greater than a predefined pixel value.

I wrote some code that takes a look at the original image, checks to

Answer 1

I did something similar for Bitmaps, but idea is same:

1. get image height and width
2. get current screen resolution
3. calculate aspect ratio (ASR) from image size

Handle following cases:

4. if ASR >=1 and image width > image height
    if image width > screen width {}
        if image height > screen height {}
        else if image width > screen width {}
    else {}
   else
    if image height > screen height {}
    else if image width > screen width {}
    else {}

//SCREEN_SIZE is configurable; Defs.SCREEN_SIZE = 100; // and boolPixelAR is true;

Try following code:

            // PERCENTAGE OF IMAGE -> TODO: Configurable? IMAZE ZOOM / SCREEN PERCENTAGE
            Double HScale = __bmp.Width;// *Defs.SCREEN_SIZE / 100;
            Double VScale = __bmp.Height;// *Defs.SCREEN_SIZE / 100;
            Double __aspectRatio;
            Double __screenRatio = _currentScreenSize.Width / _currentScreenSize.Height;

            // PERCENTAGE OF SCREEN
            if (!_boolPixelAR) {
                HScale = _currentScreenSize.Width * Defs.SCREEN_SIZE / 100;
                VScale = _currentScreenSize.Height * Defs.SCREEN_SIZE / 100;
            }
            else {
                __aspectRatio = HScale / VScale;
                if( __aspectRatio >= 1)
                    if (HScale >= _currentScreenSize.Width) {  // Long Edge is WIDTH. For 100%, HScale = WIDTH
                        VScale = ((VScale * _currentScreenSize.Width) / HScale) * Defs.SCREEN_SIZE / 100;
                        HScale = _currentScreenSize.Width * Defs.SCREEN_SIZE / 100;

                        if (VScale > _currentScreenSize.Height) {                  // Long Edge is HEIGHT. For 100%, VScale = HEIGHT
                            //__aspectRatio = VScale / HScale;
                            HScale = ((HScale * _currentScreenSize.Height) / VScale) * Defs.SCREEN_SIZE / 100;
                            VScale = _currentScreenSize.Height * Defs.SCREEN_SIZE / 100;
                        }
                    }
                    else if (VScale > _currentScreenSize.Height) {                  // Long Edge is HEIGHT. For 100%, VScale = HEIGHT
                        //__aspectRatio = VScale / HScale;
                        HScale = ((HScale * _currentScreenSize.Height) / VScale) * Defs.SCREEN_SIZE / 100;
                        VScale = _currentScreenSize.Height * Defs.SCREEN_SIZE / 100;
                    } 
                    else {
                        //Do nothing... Just set Zoom.
                        HScale = HScale * Defs.SCREEN_SIZE / 100;
                        VScale = VScale * Defs.SCREEN_SIZE / 100;
                    }
                else 
                    if (VScale > _currentScreenSize.Height) {                  // Long Edge is HEIGHT. For 100%, VScale = HEIGHT
                        //__aspectRatio = VScale / HScale;
                        HScale = ((HScale * _currentScreenSize.Height) / VScale) * Defs.SCREEN_SIZE / 100;
                        VScale = _currentScreenSize.Height * Defs.SCREEN_SIZE / 100;
                    }
                    else if (HScale >= _currentScreenSize.Width) {  // Long Edge is WIDTH. For 100%, HScale = WIDTH
                        VScale = ((VScale * _currentScreenSize.Width) / HScale) * Defs.SCREEN_SIZE / 100;
                        HScale = _currentScreenSize.Width * Defs.SCREEN_SIZE / 100;
                    } 
                    else {
                        //Do nothing... Just set Zoom.
                        HScale = HScale * Defs.SCREEN_SIZE / 100;
                        VScale = VScale * Defs.SCREEN_SIZE / 100;
                    }

                ////__aspectRatio = VScale / HScale;
                //HScale = ((HScale * _currentScreenSize.Height) / VScale) * Defs.SCREEN_SIZE / 100;
                //VScale = _currentScreenSize.Height * Defs.SCREEN_SIZE / 100;
            }

            Bitmap scaledBmp = GraphicsFactory.ResizeImage(
                                        __bmp,
                                        Convert.ToInt32(HScale),
                                        Convert.ToInt32(VScale));