how to find compression ratio of an image ?

hai,

I am working on image processing project, I need to find the compression ratio of an jpeg image. Is there any command in matlab to find the compression ratio of the image?

ARUN

Answer 1

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/27322-cr-bit-per-pixel-image-compression

Answer 2

[Jan]

No. The compression ratio is not stored in the JPEG file, as far as I know. Even commercial image software contains features to "estimate the compression level". Even if the compression level is stored in the file header, what would it mean? Imagine a photo of a blank white sheet of paper, which is compressed at first inside the camera by 95%, and then in the software by further 80%. Should the levels be multiplied?! And if the level is set to 5%, the resulting image file gets a signal to noise ratio, which is very near to the original object.

I know that there are some techniques to estimate the compression level, but this can be an approximation only.