Issue with InterpolationMode.NearestNeighbor not affecting rendering in C# application

Question

I'm working on a C# application that involves rendering images onto a PictureBox. The images are 640x640 pixels in size, and I'm drawing them onto a destination of the same size. To optimize rendering performance and prioritize speed over image quality, I've tried setting the InterpolationMode to InterpolationMode.NearestNeighbor. However, I haven't observed any noticeable change in rendering speed or image quality.

Here's the code snippet where I'm setting the InterpolationMode:

using (Graphics gfx = Graphics.FromImage(pictureBox1.Image))
{
    // Other settings...
    
    // Set the interpolation mode to NearestNeighbor
    gfx.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.NearestNeighbor;
    
    // Other drawing operations...
}

I've confirmed that the source and destination sizes are both 640x640, so there is no scaling involved. I was expecting this change to improve rendering speed, but I haven't seen a significant effect.

Is there something I might be missing or a common pitfall when using InterpolationMode.NearestNeighbor for images that aren't being scaled? Are there other factors that could be affecting the rendering performance?

I'd appreciate any insights or suggestions for troubleshooting this issue.

Additional Information:

Image size: 640x640 Destination size: 640x640 Using Windows Forms for rendering