image compression using dct

[nazneen]

Their is an example vi for image compression using DCT in Labview 2010. How to view the compressed image in that, as the example outputs only the restored image(decompressed image) and how to calculate the compression ratio for the same.

[nazneen]

Anyone who can help me out ??

[ThomasGutzler]

I know nothing about DCT compression, but I would assume that you can calculate the compression ratio: ratio = (size of new image) / (size of old image)

It's up to you how to get the sizes. You can use the amount of bytes in a file or the amount of bytes in a data structure containing the images (flatten to string + string length)

[nazneen]

After taking dct of the input image, the matrix contains values which are 16 bit unsigned. How to obtain the compressed image from this?

[hooovahh]

Topics merged, please do not make multiple threads for the same discussion.

[Rolf Kalbermatter]

After taking dct of the input image, the matrix contains values which are 16 bit unsigned. How to obtain the compressed image from this?

 

It is quite unclear to me what you try to do here. Can you provide some VI code here and explain in more detail what your problem is? If you have a 2D array of uIn16 values I would think this to be your compressed image data. This can be saved as binary stream but of course would be only useful for your application that knows through which decompressing function to run it through to get the uncompressed data again.

 

If you want to save it in a way so other applications can read it then you may be on the wrong track here. Generally while specific compression algorithms can be interesting to use, there is a lot more involved in making sure that such an image file is readable in other applications too. For that there have been specific compressable image formats such as JPEG, JPEG2K, PNG and TIFF, although TIFF is probably the worst of all in terms of interoperability as it allows in principle for an unlimited amount of image formats and compressions to be used, yet there is no application in the world which could read all possible TIFF variants.