how to change image bitmap dimensions?

Question

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C#

Bitmap img;//outside current method.
                   private void Form1_Load(object sender, EventArgs e)
                   {
                    pictureBox1.SizeMode = PictureBoxSizeMode.Zoom;
                    img = new Bitmap(file.FullName);
                    if (img.Height >= pictureBox1.Height )
                    {
                     //how do i change the img dimension?
                     //i want to Set the height or width of the loaded image, to fit it properly into my picturebox.
                     //if the image mode is vertical, my picturebox must have height> width. The height of the img will transform how high the picturebox high will be. 

                    }
                     pictureBox1.Image = img;
                   }

Posted 26-Jun-15 21:35pm

_Q12_

Updated 26-Jun-15 21:36pm

v2

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2 solutions

Solution 1

I found this on a blog some years ago, but cannot find the original. This is my modified version of the blog. It's C++ but the principles are the same, converting it to C# should not be too difficult:

C++

// get the destination co-ordinates
::GetClientRect(hWnd, &rectWindow);

destRect.X = static_cast<real>(rectWindow.left);
destRect.Y = static_cast<real>(rectWindow.top);
destRect.Width = static_cast<real>((rectWindow.right - rectWindow.left));
destRect.Height = static_cast<real>((rectWindow.bottom - rectWindow.top));

/*
 * The key to keeping the correct aspect ratio while resizing an image is the algorithm
 * used to calculate the ratio, viz.
 *
 *	NewHeight = GivenWidth * (OriginalHeight / OriginalWidth)
 * or
 *
 *	NewWidth = GivenHeight * (OriginalWidth / OriginalHeight)
 *
 * This calculation assumes that the "Given..." is the dimension the image
 * should be resized to.
 * Once we know this, we can multiply it by the original image’s aspect,
 * and that will give us the other side's value we need. So, assuming the
 * original image has a width of 1000 and a height of 1600 and we want it
 * to be resized to a width of 500:
 *
 *	First find the aspect: (1600 / 1000) = aspect of 1.6
 *	Now multiply the aspect by the desired new width: 1.6 * 500
 *	The result of that multiplication is 800, which is what our height should be
 *	In other words:
 *	800 = 500 * (1600 / 1000)
 * So the resulting image would have a height of 800 and a width of 500.
 *
 */
imageWidth =  static_cast<real>(pImage->GetWidth());
imageHeight =  static_cast<real>(pImage->GetHeight());
// if width or height is less than window, use image size
if (imageWidth < destRect.Width)
    destRect.Width = imageWidth;
if (imageHeight < destRect.Height)
    destRect.Height = imageHeight;

if (imageWidth > destRect.Width)
{
    // if wider than window then adjust height by aspect ratio
    aspect = imageHeight / imageWidth;
    REAL newHeight = destRect.Width * aspect;
    // but don't make it deeper than the window
    if (newHeight <= destRect.Height)
        destRect.Height = newHeight;
}
if (imageHeight > destRect.Height)
{
    // if deeper than window then adjust width by aspect ratio
    aspect = imageWidth / imageHeight;
    destRect.Width = destRect.Height * aspect;
}

Posted 26-Jun-15 22:25pm

Richard MacCutchan

v2

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_Q12_ · Accepted Answer · 2015-06-26T23:35:00

it seem i got a stroke of geniality...:)
i used the three rule.
And is working perfectly... yuhoo.

C#

                    uc.pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
                    img = new Bitmap(item.FullName);
                    uc.pictureBox1.Image = img;
                    if (img.Height >= uc.pictureBox1.Height)
                    {
                        //10/5 = 8/x  >> x= (8*5)/10 >> x=4   (10/5=2, 8/4=2)
                        uc.Height = (uc.pictureBox1.Width * img.Height) / img.Width;
                    }
// where uc = userControl that contain a public pictureBox1.