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Asked: 2026-05-20T01:21:33+00:00

I have some code that creates a graph using the Bitmap class. The quality

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I have some code that creates a graph using the Bitmap class. The quality of the produced bitmap, however, is pretty poor, how can I improve the quality of this? Note that I am using the Compact Framework!

Here is a few snippets of how I do various things:

Create a bitmap with a background based on an existing jpg

Bitmap bitmap = new Bitmap(filename);

I then create a Graphics class from the bitmap

Graphics myG = Graphics.FromImage(bitmap);

I then draw to the graphics like so:

myG.DrawLine(majorAxisPen, graphRect.Left, graphRect.Bottom, graphRect.Right, graphRect.Bottom);

After drawing everything I need to I then save out the Bitmap like so:

bitmap.Save(fileDestination, System.Drawing.Imaging.ImageFormat.Jpeg);

Here is the image it produces
Poor quality image

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1 Answer

  1. Editorial Team

    There are two sources of “low quality” you may encounter.

    1. The actual drawing to the graphics object may be low quality – i.e. the lines you draw may be aliased (pixelated).
    2. The low quality can be a side effect of the jpeg encoding when you output the graphics to a stream.

    Every Graphics object has a number of properties that control the “quality” of the operations you can perform on the object. In particular, you should set SmoothingMode to HighQuality to avoid jaggies on line drawings. Unsupported in .NET Compact Framework.

    To avoid compression artifacts, you can control jpeg compression parameters by manually controlling compression rather than using the (low-quality) default ImageFormat.Jpeg – unfortunately, doing so on CF is not possible without resorting to manual P/Invoking or a third party library. For a more extensive code sample for the full .NET Framework, see an answer I wrote to a similar question: How do you conver a HttpPostedFileBase to an Image?.

    An easy alternative is to use use PNG, a lossless image format that does not degrade quality each time it is saved – given the simple geometric shapes of the example you posted, this won’t even cost you anything in terms of file-size. Using another format may be your only option; customizing jpeg encoder parameters isn’t possible in the Compact Framework since the ImageCodecInfo isn’t available. If you really need Jpeg, you could attempt to use an external library (e.g. http://www.opennetcf.com/library/sdf/), or P/Invoke native methods directly to access platform-specific encoders.

    Some possible approaches for anti-aliasing:

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