size of bitmap in drawImage

Question

I've asked question on proper scaling without rim on right and bottom. link

I've checked and size of bitmap is 32 by 32 pixels. When i try to draw it on pictureBox with drawImage(Image, int, int) it draws it little bit bigger than size of bitmap like 36 by 36 or 40 by 40. Not sure. But when i add width and height to drawImage it draws it 32 by 32. Is this supposed to happend.

Edit:

    internal void draw(Graphics g, int x, int y)
    {
        int s = Game.scale;
        Bitmap resized = (s > 1) ? ResizeImage(image, width*s, height*s) : image;

        g.DrawImage(resized, x * width * s, y * height * s);
    }

    private static Bitmap ResizeImage(Image image, int width, int height)
    {
        var destRect = new Rectangle(0, 0, width, height);
        var destImage = new Bitmap(width, height);
        destImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);

        using (var graphics = Graphics.FromImage(destImage))
        {
            graphics.CompositingMode = CompositingMode.SourceCopy;
            graphics.CompositingQuality = CompositingQuality.HighQuality;
            graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
            graphics.SmoothingMode = SmoothingMode.HighQuality;
            graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;

            using (var wrapMode = new ImageAttributes())
            {
                wrapMode.SetWrapMode(WrapMode.TileFlipXY);
                graphics.DrawImage(image, destRect, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, wrapMode);

            }
        }

        return destImage;
    }

Where does `draw` get called? What is the value of `Game.scale`? I don't see anything about a PictureBox in this code. — Equalsk, Dec 07 '17 at 11:51

score 4 · Accepted Answer · answered Dec 07 '17 at 12:20

Feature, not a bug. If you don't specify the target size then DrawImage() pays attention to the physical size of the image. The size it had when it was created, in inches. Something you can see back in the debugger, look at the bitmap's HorizontalResolution and VerticalResolution properties.

With the diagnostic that it is probably 120 dots-per-inch, programmers commonly run their video adapter at 125% today. So the drawn image becomes 1.25 * 32 = 40 pixels.

Keep in mind that this kind of rescaling tends to be important, such an image can easily turn into but a fleck of dust on an upscale 4K monitor. They are getting pretty affordable today. Whether you want this or not depends on how the rest of your UI rescales. Check out this post about dpiAwareness in a Winforms app.

size of bitmap in drawImage

1 Answers1

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