Resize and Save Multiple Images in C#

We'll develop an application in which user can select multiple images by "OpenFileDialog" and copy those images to specific directory after resizing it.

• Open visual studio and create new "Windows Form Application" project.
• Go to Toolbox and drag a button.
• Change name of button to "FileUploadBtn".
• Change text of button to "Upload & Resize Images".
• Now double click at that button and add following code in its click event

private void FileUploadBtn_Click(object sender, EventArgs e)
{
    OpenFileDialog openFileDialog = new OpenFileDialog();

    //Add filter, if you want to allow all extenssions just remove it.
    openFileDialog.Filter = "Images (*.BMP;*.JPG;*.GIF)|*.BMP;*.JPG;*.GIF|" + "All files (*.*)|*.*";

    // Set multiselect true for slecting multiple files
    openFileDialog.Multiselect = true;
          
    // Show open file dialog and check if Open button is pressed.
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        // Set directory name and create it.
        string directory = "Files";

        Directory.CreateDirectory(directory);

        // Read all files.
        foreach (string fileName in openFileDialog.FileNames)
        {
            // Get file name without its path.
            string newFile = directory + "/" + Path.GetFileName(fileName);

            ResizeImage(fileName, newFile, 100, 100, true);
        }
    }
}

Now we have to add function "ResizeImage"which will responsible for resizing image and saving it.

public void ResizeImage(string originalFile, string newFile, int NewWidth, int MaxHeight, bool OnlyResizeIfWider)
{
    Image OriginalImage = Image.FromFile(originalFile);

    if (OnlyResizeIfWider)
    {
        if (OriginalImage.Width <= NewWidth)
        {
            NewWidth = OriginalImage.Width;
        }
    }

    int NewHeight = OriginalImage.Height * NewWidth / OriginalImage.Width;
    if (NewHeight > MaxHeight)
    {
        // Resize with height instead
        NewWidth = OriginalImage.Width * MaxHeight / OriginalImage.Height;
        NewHeight = MaxHeight;
    }

    Image NewImage = OriginalImage.GetThumbnailImage(NewWidth, NewHeight, null, IntPtr.Zero);

    // Save resized picture
    NewImage.Save(newFile);

    // Clear handle to original file so that we can overwrite it if necessary
    OriginalImage.Dispose();
    NewImage.Dispose();
}

Now run the application and test it. It will create a directory named "Files" to your application's "bin/Debug"directory and save resized images in that new created directory.

 

  

"GetThumbnailImage" is the key methodfor generating a thumbnail and "NewImage.Save()" is the key method for saving that thumbnail. Click at links to see their more details