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Troubleshooting Question

How do I make an image transparent?

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Last Modified: 2020-10-23
I have Photoshop.   I want to compare two images by overlaying one on the other.   How do I make one of them transparent so I can spot differences when they are overlaid?
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David FavorFractional CTO
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Distinguished Expert 2019

Commented:
First you must start with an image format that supports transparency - PNG or GIF.

Or you can simulate transparency if you know your site's background color will never change - SVG + JPEG + most other formats - by matching background pixels to site background default, like black or white.

Comparing layers by overlapping them. Well... I suppose if you have a recent model Borg implant you might be able to eyeball this... likely not though...

Without having actual images to work from, it's difficult to guess what you might be describing.

Generally: To convert a non-transparent image to transparency, you'll blow up the image + edit pixels, flipping all pixels to one color (usually black or white), the export the image into a PNG or GIF format specifying to convert one color (usually black or white) into the transparent layer.

Not overly complex. Just grueling + time consuming work for large images with many edges, especially with blended colors at region edges, where choices have to be made about exactly what pixels to change to your transparency color.

Author

Commented:
I am attaching the type of JPEG image I want to compare.   I thought it might be possible to just make one of them transparent so I could place on on top of the other and compare them.
David FavorFractional CTO
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Distinguished Expert 2019

Commented:
This will be tough, as these appear to be from different animals (counting ribs) + are labeled as the same animal.

You'd have to somehow stretch these over each other + try to overlay them.

Maybe turning black into transparent + using them as overlays, then flipping between them might work.

Author

Commented:
They are the same animal, just x-rays at different times, which is why I wanted to be able to compare them.   I do not know how to overlay them.
David FavorFractional CTO
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Distinguished Expert 2019

Commented:
Good question.

I'm unsure about how to do this.

You almost need a light box where you can adjust the distance between the 2x X-Rays.
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