C# Forms Print Image As Big As Possible

Question

I want to print an image on Windows Forms, but I want to print the image as big as possible on the page without breaking its aspect ratio. Like when I want to print a simple square to A4 paper it becomes rectangle with this script:

private void Page(object sender, PrintPageEventArgs e)
{
    Bitmap i = image;
    if(e.PageBounds.Height > e.PageBounds.Width)
    {
        if (i.Width > i.Height)
            i.RotateFlip(RotateFlipType.Rotate90FlipNone);
    }
    else if(e.PageBounds.Width > e.PageBounds.Height)
    {
        if (i.Height > i.Width)
            i.RotateFlip(RotateFlipType.Rotate90FlipNone);
    }
    e.Graphics.DrawImage(i, new Rectangle(0, 0, e.PageBounds.Width, e.PageBounds.Height));
    i.Dispose();
}

Original: 500x500 square

What I got (as pdf): A rectangle on the A4 paper

Another example:

Original:Original image(313x234)

Print:Print image

I don't want to break the aspect ratio of the image

I take it you mean the aspect ratio, not the resolution or "solution"? — NetMage, Sep 17 '18 at 16:44
@NetMage Thanks for the information! I edited my post by replacing (re)solution with aspect ratio. Thanks again for your help by making my post cleaner — Mr. Deniz, Sep 17 '18 at 16:55
And now if you search for resize while preserving aspect ratio, you should find [this answer](https://stackoverflow.com/a/2001692/2557128) — NetMage, Sep 17 '18 at 16:57

Joel Coehoorn · Answer 1 · 2018-09-17T17:35:37.193

Try this:

private void Page(object sender, PrintPageEventArgs e)
{
    using (Bitmap i = image)  //are you *really sure* you want to dispose this after printing? 
    {
        var pageRatio = e.PageBounds.Width / (double)e.PageBounds.Height;
        var imageRatio = i.Width / (double)i.Height;

        //do we need to rotate?
        if ( (pageRatio < 1 && imageRatio > 1) || (pageRatio < 1 && imageRatio > 1))
        {
            i.RotateFlip(RotateFlipType.Rotate90FlipNone);
            imageRatio = i.Width / (double)i.Height; //ratio will have changed after rotation
        }         

        var scale = 1.0D;
        //do we need to scale?
        if (pageRatio > imageRatio)
        { //the page is wider than the image, so scale to the height
             scale = e.PageBounds.Height / (double)i.Height;
        }
        else if (pageRatio < imageRatio)
        { //the page is narrower than the image, so scale to width
            scale = e.PageBounds.Width / (double)i.Width;
        }

        var W = (int)(scale * i.Width);
        var H = (int)(scale * i.Height);

        e.Graphics.DrawImage(i, new Rectangle(0, 0, W, H));
    }
}

This will always draw from the top left corner. If you want it centered, you need to make additional adjustments:

private void Page(object sender, PrintPageEventArgs e)
{
    using (Bitmap i = image)  //are you *really sure* you want to dispose this after printing? 
    {
        var pageRatio = e.PageBounds.Width / (double)e.PageBounds.Height;
        var imageRatio = i.Width / (double)i.Height;

        //do we need to rotate?
        if ( (pageRatio < 1 && imageRatio > 1) || (pageRatio < 1 && imageRatio > 1))
        {
            i.RotateFlip(RotateFlipType.Rotate90FlipNone);
            imageRatio = i.Width / (double)i.Height; //ratio will have changed after rotation
        }         

        int T = 0, L = 0; //top, left
        var scale = 1.0D;
        int W = i.Width, H = i.Height;

        //do we need to scale?
        if (pageRatio > imageRatio)
        { //the page is wider than the image, so scale to the height
             scale = e.PageBounds.Height / (double)i.Height;
             W = (int)(scale * i.Width); 
             H = (int)(scale * i.Height);
             L = (e.PageBounds.Width - W)/2;
        }
        else if (pageRatio < imageRatio)
        { //the page is narrower than the image, so scale to width
            scale = e.PageBounds.Width / (double)i.Width;
            W = (int)(scale * i.Width); 
            H = (int)(scale * i.Height);
            T = (e.PageBounds.Height - H)/2;
        }

        e.Graphics.DrawImage(i, new Rectangle(L, T, W+L, H+T));
    }
}

The important thing is both the width and height are adjusted to the same scale... that is, multiplied by the same number.

First thanks for your code but sorry, it didn't worked. It still breaks the aspect ratio. NetMage's answer helped me to solve it — Mr. Deniz, Sep 17 '18 at 17:11
There was a bug in my 2nd sample that should be correct now. — Joel Coehoorn, Sep 17 '18 at 17:37

C# Forms Print Image As Big As Possible

1 Answers1