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Matching Jpeg Artifacts and Pixelation - not removal - How to?

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Marc Nibor
Matching Jpeg Artifacts and Pixelation - not removal - How to?
on Jul 7, 2011 at 2:18:14 pm

Hi,

I need to ADD pixelation and artifcats to a few images in order to match the qualitiy to an existing (bad) background image.

it's a Photograph of a table in a livingroom and i need to place/add some fruits and a bottle on the table.

The image is 1600x1080 which actually whouldn't be too bad. but it was just sized up from an already quite bad jpeg with lots of artifacts. At this moment it is not possible to use a different image. I HAVE to work with what I've got.

When I add the fruits and bottle they totally stand out - because they have just too much detail compared to the background.
I already resaved them at the lowest jpeg setting - but somehow it still doesn't look right. I also tried all the pixelate filters in PS


What are the best ways to match the quality in such a case?
I only found ways to remove artifacts.... but not anything to add them in a controlled way.
I think I saw and addon/plugin that does something like that, but I cannot remember exactly.



another thing:
what is a good way to deal with highlights and lightangles when matching images and the light "directions" do not match?



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Emily Carmichael
Re: Matching Jpeg Artifacts and Pixelation - not removal - How to?
on Jul 9, 2011 at 3:24:22 pm

My first piece of advice would definitely have been to save the fruit and bottle at the lowest JPEG setting--you can also experiment with some of the other compression modes in the "Save for Web and Devices" dialogue. But, different images (and sizes of images) will acquire different artifacts upon compression.

Other things that you can try:

-Playing with the levels--I suspect the real reason why your images are standing out is because they are crisper and seem to have more contrast. Tweak the levels to wash them out a little more.
-Adding noise (filters>noise>add noise)
-Make sure the mask around your images is appropriately soft (so they don't have a crisp line around them.)

Here's what I would do for light angles.

-First: can I ignore them? Movie posters are full of mismatched light angles that no one ever notices.
-Second: Can I flip one of the images to better approximate the desired angle?
-If those fail, I like the Dodge tool to add highlights. Dodging Highlights produces a bright highlight (like hair or metal would have,) Dodging Midtones produces a less saturated highlight. To add shadows, you can use the Burn tool, or create a new layer with the blend mode set to Multiply and just paint some shadows on. Just choose the most obvious aspect of the lighting scheme and add a highlight or shadow or two to match--don't focus on reversing it completely.

And of course, you'll need new shadows for the objects you're adding (and/or reflections, if the table is shiny.)


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Marc Nibor
Re: Matching Jpeg Artifacts and Pixelation - not removal - How to?
on Jul 10, 2011 at 2:33:06 am

Thank you very much Emily for this detailed answer.

I came close with the artifacts... but just resaving was not enough. I actually ended up to size down (transform) and size up the fruits over and over until the quality was matching.

As for the levels... changing the levels alone was not enough. after trying out alot of other things I found that changing the vibrance worked best.

I did not get any satisfying results with the lightangles yet, so I will try out all your suggestions asap -

again.... thank you very much for your effort.

Marc



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Nikita Zhekova
Re: Matching Jpeg Artifacts and Pixelation - not removal - How to?
on Jan 29, 2014 at 2:52:24 pm

I have a photo whose background needed blurring out, to simulate shallower depth of field. compared to adjacent areas unblurred, the blurred area was far too smooth. the rest of the photo contains pixelation as per jpeg lossy compression.
filter -> noise -> add noise didn't do the needed job of matching the two adjacent areas. the speckles were a good start, but were too small. altering their percentage, the only available option, didn't help.

However if you go to filters -> artistic -> paint daubs
and use a wide blurry brush,

adjusting the size of the texture to match the other areas of the photo, you get an approximation, though the resulting texture is slightly contorted to bestow 'spontaneity'.

seems legit


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