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c#graphicsgdi+interpolationstretch
Nick
Nick

Reputation: 749

c# Draw Image (Scaled) to Graphics, does not interpolate correctly. Fixes?

I have an image that is 1px wide, and some height. I need to draw this image across the entire width of the control on it's OnPaint event. I get it to draw, however not correctly. It seems like when it stretches it, it doesn't actually fill all the pixels. As if the interpolation is off. Is there a way to say "stop being smart, just draw it already"? I see no InterpolationMode.Off or .None in the options for the graphics object.

I can confirm I actually drawing the full width by using an image of width X where X is the same width as the control. Then when it draws, it covers the full area as normal. However this control is resized all the time, and to save memory and all that jazz using 1px wide images is quite normal in the web world. This is for a desktop C# application though. Any ideas on how to fix this?

Upvotes: 5

Views: 3896

Answers (2)

Nick
Nick

Reputation: 749

Ok I figured out the magic keywords:

g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.Half;

This coupled with setting the Interpolation Mode to NearestNeighbour allows for a full block to be drawn.

Without setting the Interpolation mode, you get weird blending (expected). Without setting the PixelOffsetMode, the nearest neighbour algorithm has no neighbour to compare to on a blank paint and therefore only draws half the image, for half the width. Setting it to offset half, moves everything over by -0.5px, and allows this algorithm to work for block textures.

Upvotes: 13

Ed Swangren
Ed Swangren

Reputation: 124642

InterpolationMode.NearestNeighbor is what you want to use in this case.

Upvotes: 0

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