Image is not drawn at the correct spot

Question

Bitmap image = ReadBitmap("image.png");
Bitmap imageCopy = new Bitmap(image);
Bitmap canvas = new Bitmap(imageCopy.Width+100, imageCopy.Height);

// From this bitmap, the graphics can be obtained, because it has the right PixelFormat
using(Graphics g = Graphics.FromImage(canvas))
{
    // Draw the original bitmap onto the graphics of the new bitmap
    g.DrawImage(image, 0, 0);
}

// Use tempBitmap as you would have used originalBmp
InputPictureBox.Image = image;
OutputPictureBox.Image = canvas;   

I haven't understood the output of this c# code.

The original image is not placed at the correct position. It should have been at (0, 0). Also, I need a black background.

So, what is going on and how to correct this?

Answer 1

You are loading an Image, then a copy of this source is created using:
Bitmap bitmap = new Bitmap();

When you create a copy of an Image this way, you sacrifice/alter some details:
Dpi Resolution: if not otherwise specified, the resolution is set to the UI resolution. 96 Dpi, as a standard; it might be different with different screen resolutions and scaling. The System in use also affects this value (Windows 7 and Windows 10 will probably/possibly provide different values)
PixelFormat: If not directly copied from the Image source or explicitly specified, the PixelFormat is set to PixelFormat.Format32bppArgb.

From what you were saying, you probably wanted something like this:

var imageSource = Image.FromStream(new MemoryStream(File.ReadAllBytes(@"[SomeImageOfLena]"))), true, false)
var imageCopy = new Bitmap(imageSource.Width + 100, imageSource.Height, imageSource.PixelFormat))

imageCopy.SetResolution(imageSource.HorizontalResolution, imageSource.VerticalResolution);
using (var g = Graphics.FromImage(imageCopy)) {
    g.Clear(Color.Black);
    g.CompositingMode = CompositingMode.SourceCopy;
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;
    g.DrawImage(imageSource, (imageCopy.Width - imageSource.Width) / 2, 0);

    pictureBox1.Image?.Dispose();
    pictureBox2.Image?.Dispose();
    pictureBox1.Image = imageSource;
    pictureBox2.Image = imageCopy;
}

This is the result:
(The upper/lower frame black color is actually the Picturebox background color)

When the original Image Dpi Resolution is different from the base Dpi Resolution used when creating an Image copy with new Bitmap(), your results may be different from what is expected.

This is what happens with a source Image of 150, 96 and 72 Dpi in the same scenario:

Also, possibly, don't assign an Image object directly loaded from a FileStream or - way worse - using Image.FromFile() (slow, ignores ICM unless instructed: nobody ever does it)
GDI+ will lock the file, and you will not be able to copy, move or delete it.
With the file, all resources tied to the Images will also be locked.

I suggest using the Image.FromStream(Stream, Boolean, Boolean) overload, passing a MemoryStream, filled calling File.ReadAllBytes(). E.g.,

var image = Image.FromStream(new MemoryStream(File.ReadAllBytes([Image Path])), true, false);  

This instructs to consider embedded ICM information (when present) to preserve the colors and to bypass data validation (this speeds up the process quite a bit)

Image.Clone() can also be used to duplicate an Image, it will preserve the Image Dpi Resolution and PixelFormat.

Another important detail is the IDisposable nature of the Image object.
When you create one, you have to Dispose() of it; explicitly, calling the Dispose method, or implicitly, enclosing the Image contructor in a Using statement.