CODEWITHSUNDEEP
c#image-processing
Andrew Simpson
Andrew Simpson

Reputation: 7344

Preserving Image quality

I have a winform C# desktop application.

I have a constant stream of jpegs coming in. I am comparing the current image with the previous 1. By using a 3rd party tool - Emgu - I can create a new image that contains just the differences.

I then convert that image to a memory stream and then to a byte array.

In the receiving application I take this byte array and load the image via a memory stream using these bytes.

The trouble is that the image degrades quite a lot.

If I save the image to the hard drive before converting it to a memory stream on the client side the quality of the image is good.

The problem lies when i load it as a memory stream.

I encode it as jpeg.
If I encode it as a PNG before sending to the server the quality is good again. The trouble with encoding to PNG the size in the byte array shoots up.

What my intention was all along was to reduce the number of bytes I have to upload to improve response time.

Am I doing something wrong or can this not be done?

This is my code:

Bitmap imgContainingDifference
    = GetDiffFromEmgu(CurrentJpegImage, PreviousJpegImage);

using (System.IO.MemoryStream msIn = new System.IO.MemoryStream())
{
  holding.Save(msIn, System.Drawing.Imaging.ImageFormat.Jpeg);
  data = msIn.ToArray();
}

//test here
using (System.IO.MemoryStream msOut = new System.IO.MemoryStream(_data))
{
   Bitmap testIMG = (Bitmap)Image.FromStream(msOut);
}

//result is image is poor/degrades

If I do this instead:

using (System.IO.MemoryStream msIn = new System.IO.MemoryStream())
{
  holding.Save(msIn, System.Drawing.Imaging.ImageFormat.Png);
  data = msIn.ToArray();
}

using (System.IO.MemoryStream msOut = new System.IO.MemoryStream(_data))
{
   Bitmap testIMG = (Bitmap)Image.FromStream(msOut);
}

//Image is good BUT the size of the byte array is 
//10 times the size of the CurrentFrame right at the start.

This is what the image looks like when using the kid suggestion from :

enter image description here

I have now tried using a encoder from the kind suggestion from @MagnatLU and I also get the same quality of image if I use FreeImage.Net.

Upvotes: 4

Views: 2394

Answers (1)

user418938
user418938

Reputation:

You can set JPEG compression level when encoding your file to value that is the best empirical tradeoff between quality and size.

Upvotes: 5

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