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Creating High Quality Images with C# and GDI

Thursday, August 13th, 2009

I have posted in the past about creating organizational charts using C# and GDI, but I have recently come across a scenario in which I needed to make the charts show up as 100% quality (they were blurred because of the default, lower-quality GDI output).

Low and behold GDI does indeed support the ability to change output quality to a Bitmap, and while it isn't the easiest thing to figure out originally, it really isn't that bad.

So I figure the best way is to jump right into the code, so here we go. All of these classes are available in the System.Drawing.Imaging namespace of .NET:

// Encoder parameters can hold multiple parameters to pass to the Save method for the Bitmap class
EncoderParameters encoderParams = new EncoderParameters();

// Requires an array for the quality parameter
long[] quality = new long[1];

// 100 is 100%, 0 is 0%
quality[0] = 100;

// Create a new encoder parameter with the specified quality array from above
EncoderParameter qualityParam = new EncoderParameter(Encoder.Quality, quality);

// Add this parameter to the entire collection
encoderParams.Param[0] = qualityParam;

// This could either be a newly-created Bitmap, or come from a loaded image, etc
Bitmap result = GetBitmapOutput();

// We can no longer pass the normal ImageFormat Enum to the Save method, so we need to find the actual encoder from C#/GDI
ImageCodecInfo[] ici = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo encoder = null;

// Loop through them all and set the encoder if we find it to be on JPEG, this could also be used for PNG, GIF, etc
for (int a = 0; a < ici.Length; a++)
if (ici[a].FormatDescription.Equals("JPEG"))
encoder = ici[a];

// Save the Bitmap to the output stream (in my case), with the specified encoder and encoder parameters
result.Save(Response.OutputStream, encoder, encoderParams);

// Clean up

Not too bad, hopefully that will help some of you along the way.

Imagin' Tom Out.


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