Question

I need to separate multiframe tiff files, and use the following method:

public static Image[] GetFrames(Image sourceImage)
{
    Guid objGuid = sourceImage.FrameDimensionsList[0];
    FrameDimension objDimension = new FrameDimension(objGuid);
    int frameCount = sourceImage.GetFrameCount(objDimension);
    Image[] images = new Image[frameCount];
    for (int i = 0; i < frameCount; i++)
    {
        MemoryStream ms = new MemoryStream();
        sourceImage.SelectActiveFrame(objDimension, i);
        sourceImage.Save(ms, ImageFormat.Tiff);
        images[i] = Image.FromStream(ms);
    }
    return images;
}

It works fine, but if the source image was encoded using the CCITT T.6 compression, separating a 20-frame-file takes up to 15 seconds on my 2,5ghz CPU.(One core is at 100% during the process)

When saving the images afterwards to a single file using standard compression (LZW), the separation time of the LZW-file is under 1 second.

Saving with CCITT compression also takes very long.

Is there a way to speed up the process?

edit:

I have measured the execution times:

        sourceImage.SelectActiveFrame(objDimension, i);
        sourceImage.Save(ms, ImageFormat.Tiff);

These two calls each account for around 50% of the total processing time.
Using one MemoryStream with an initial capacity big enough for all images results in no measurable speed gain.
The Image.FromStream method takes barely any processing time.

I need the single frames because I need to process them(deskew, rotate, etc.).

If there is a completely different method than mine, I would be happy to hear it.

Answer 1

It seems to be a problem with GDI+ on Windows 7.

I ran a sample program on a much slower machine with Windows XP, and got much better performance on compressed images than I got with Windows 7(around 2-3 times faster)