Null testing for Graphics/Images ???

[SonicMax]

Crew...

In the digital audio world...when we need to find out if one .wav file, for example, is bit-for-bit identical to another .wav file...we open both files in any audio editor or DAW, reverse the polarity of one of the files; & hit playback. if the files are identical...there is dead silence. (we also have bit meters in some apps that will show bit activity down to a noise floor of -144dB...so if there is no bit activity on the meter w/ the flipped files playing back, it serves as a true analytical test that the files are identical.)

So...do we have anything like this in the graphics world? Is there any such thing as a null test for say, two .tiff files, to see if they are exactly the same (contain precisely the same data.)

Sure would like to know if there is. I have a color corrected digital photo file that came back from the prepress dept. of my CD replication plant; & I need to be able to check if it's the same one I sent them 6 months ago (& my old graphics mgr. is gone.)

Thanks,

Sonic Max

 

[jimoblak]

Take the two images and layer them on top of each other. On the top layer, use Image->Invert to invert the colors. Set the opacity for that layer to 50%.

If the result is a fill of the same gray tone (dead silence), you have identical images.

For fun, try using the move tool and then shift the top layer a few pixels left and down by nudging the arrow keys.

 

[SonicMax]

Jim...

Thanks...will try.

Is there any such thing as a file comparison utility around, that looks at both in the form of data?

Thanks,

Sonic Max

 

[jimoblak]

You can always compare the byte sizes of both files. If they are the same, then the images are probably the same.

If you use Windows, you can get WinMerge from sourceforge.net

This program is typically used to compare text files but it can also look at binary image files. It will either say that the binary files are the same or that they are different.