Question

I’ve got this code:

    public void rotateRocketImage()
    {
        Bitmap b = this.rocketImgOriginal;

            //create a new empty bitmap to hold rotated image
        Bitmap tempBitmap = new Bitmap(97,97);

            //make a graphics object from the empty bitmap
        Graphics g = Graphics.FromImage(tempBitmap);

            //move rotation point to center of image
        //g.TranslateTransform(48, 48);

            //rotate
        //g.RotateTransform(this.orient);

            //move image back
        //g.TranslateTransform(-48, -48);

            //draw passed in image onto graphics object
        g.DrawImage(b,0,0);

        this.rocketImg = tempBitmap;
    }

which ( with RotateTransform currently disables ) should just make this.rocketImg equal to this.rocketImg , yet somehow it enlarges the picture almost twice… any ideas what could be causing it?

Thanks!

edit:
here’s the drawing code:

        private void timer1_Tick(object sender, EventArgs e)
    {
        Invalidate();
    }


    protected override void OnPaint(PaintEventArgs e)
    {

        var tempRocket = new Bitmap( rocket.rocketImg );

        using (var g = Graphics.FromImage(tempRocket))
        {
            e.Graphics.DrawImage(tempRocket, 150, 150);
        }

    }

Answer 1

There is a resolution parameter in bitmap image.

If your bitmaps have different resolutions you receive the deformation when draw one image on other.

See HorizontalResolution and VerticalResolution properties and SetResolution method of Bitmap instance.

Code sample which shows how it work:

        int magnificationIndex = 2;

        Bitmap tempRocket = new Bitmap("ccc.bmp");

        Bitmap tempBitmap = new Bitmap(97, 97);

        tempBitmap.SetResolution(tempRocket.HorizontalResolution * magnificationIndex,
            tempRocket.VerticalResolution * magnificationIndex);


        using (Graphics g = Graphics.FromImage(tempBitmap))
        {
            g.FillRectangle(Brushes.White, 0, 0, 97, 97);
            g.DrawImage(tempRocket,0,0);
        }

        tempBitmap.Save("result.bmp");