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I am working with ImageMagick (Version 7.0.7-36 Q16 x64 2018-05-29) on Windows 7. I am trying to convert a 32 bit tiff to a png.

magick.exe convert a_32bit.tif a.png

However, the resulting image looks darker than the original tiff. I had the same result with jpgs and 8 bit tiffs. Obviously some information has been lost, so I played with the "-gamma" and "-quality" flags to no avail.

I did have good results in Photoshop. I set the bit depth to 8 (Image->Model->8 bits/Channel). A warning dialog popped up stating that reducing the document depth can affect the appearance of layered HDR images. The dialog asked me if I wanted to merge layers before changing depth. I selected "Don't Merge". Then I saved the file out as a jpg. The color was fine.

Any idea how to replicate this in ImageMagick? I want to script converting these tiffs to either a jpgs or pngs.

Thanks.

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  • Sounds like a Color Management issue. is a colour profile embedded in the files? If not, what colour setup do you have in Photoshop and ImageMagick ?
    – cybernetic.nomad
    Commented Jun 1, 2018 at 17:26

2 Answers 2

Reset to default
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Interesting. Applying a gamma correction of 2.2 does the trick.

magick.exe convert a_32bit.tiff -gamma 2.2 a.jpg

I thought I wouldn't have to do this if the image was in the sRGB color space.

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  • Well, in theory, you mustn't. In practice, every app has its quirks.
    – user477799
    Commented Jun 2, 2018 at 5:52
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Since you've got good results in Photoshop, you could create an action to record the steps you have described and then apply this action to all TIFF using the batch process.

Here is a link to a tutorial about this.

https://www.youtube.com/watch?v=TzBws9yIeR8

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