SikuliX

Mac: colors slightly darker in screenshots than original in VMBox/Windows

Asked by ash

I made several screenshots with the following command:

capture(some_region)

All is fine, but some colors in those screenshots are slightly wrong - little darker than original.

Could it be that compression in PNG files is too extreme? Can I change quality settings for PNG files?

I am using Mac Sikuli X-1.0rc3. It controls Windows application running in VirtualBox VM.

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RaiMan (raimund-hocke) said : 		#1

Did you check the RGB values of these pixels or is it only some visual impression?

The rendering engine in the Windows VM environment might produce differences against the same image on Mac, caused by the specific Mac behavior with color spaces towards the monitor.

So if you want to be sure, you have to check the RGB values of the same pixel in both environments.

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ash (shamrin) said : 		#2

Thank you for reply, RaiMan!

I haven't checked RGB values, but the difference is pretty visible.

Mac Sikuli: http://i.imgur.com/c7bUV.png
Windows Sikuli (app and Sikuli both run inside VirtualBox): http://i.imgur.com/Fyggh.png

As you can see the first image is visibly darker that the second.

And just to make sure the issue is Sikuli-specific, I made the the screenshot with Mac Screen Capture: http://i.imgur.com/OTR5x.png

It's has correct (lighter) colors.

In the end I moved my Sikuli script to Windows and made correctly colored screenshots with it.

But the original issue is still there. Why the colors are wrong with my original setup? Probably a Sikuli bug?

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RaiMan (raimund-hocke) said : 		#3

confirmed:
c7bUV (Mac Sikuli) is slightly darker against the others which are identical. This applies to the color of all pixels.

I made a comparing test on my Mac Lion having Win7 in Parallels and the images produced with Sikuli running on Mac (I used the Crome icon in Windows) either with IDE's capture feature or with Screen.capture() are slightly darker, than the images produced with Sikuli running on Windows and with Mac's capture feature.

What finally really surprises:
Running the script on Mac ALL the Mac images produce a score of 1.0 but the Windows images produce 0.9 only
On Windows the situation is vice versa: Win images bring 1.0, the Mac images 0.9
And always the darker images bring the same score as the normal image in both cases.

This is definitely a buggy situation.

And I just realized: On Mac this is generally the case: images captured with the Sikuli features are slightly darker than the originals (but this does not seem to affect the searching as such).

Can you help with this problem?

Provide an answer of your own, or ask ash for more information if necessary.

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