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Resizing image causes pixellation, jagged image, but...

Posted on 2006-07-20
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Last Modified: 2008-01-09
This is something about PhotoShop 7.0 that has been bothering me for a while.

If I load an image from a file and then go to IMAGE > IMAGE RESIZE and then resize the image proportionally to a smaller pixel width/height, using the default bicubic resampling, the image appears jagged and pixellated.

However, a "trick" I learned to overcome this was to load the image file, then use my selection tool to select the entire image, copy it, paste that into a new instance and THEN resize that, the reduced image is NOT pixellated or jagged.  It's almost as if the very act of taking this extra step activates some sort of antialiasing that hadn't been active by default.

Why must I jump through this hoop to avoid the jagged image results?  Is there something I'm missing? Any way to achieve the same results without jumping through that extra hurdle?  Or is this a well known "flaw" in PhotoShop?
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Question by:cacklebunny
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lherrou earned 100 total points
ID: 17146100
Cacklebunny,

No, this isn't a flaw in Photoshop. First of all, are you making sure your image is in RGB or CMYK format before resizing? Go to Image -> Mode and see where the checkmark is, to find out. If you are using a more limited color space (for example, a .GIF file), you will have this problem because Photoshop can't produce the interim shades of color to keep the edges smooth. Also, make sure you are viewing it at 100% (actual pixels), because sometimes when you are resizing an image you start with a large image which won't fit on screen, so you are viewing at 57% or something like that, and when you re-size, you are still viewing at 57% even though the new, smaller image WOULD fit on screen - but if you aren't viewing at full size, it can look pixelated/jaggy.

Cheers,
LHerrou
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Expert Comment

by:Festaman
ID: 17148461
Hello lherrou,

The best plugin i found for enlarging images with no distortion or pixelation is Called Genuine Fractals it works up to about a 700% enlargement. It works great! There is a free trial on there web site.  If you google Genuine Fractals trial you should find it i believe the company is called LizardTech. I think the product is discontiuned but its works excelent

Good Luck!
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by:lherrou
ID: 17148560
Festaman,

I've used GF, and have on occasion recommended it for Askers here on Experts Exchange. However, in this case, the Asker (Cacklebunny) is having trouble DECREASING the image size, not increasing...

LHerrou
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by:YoungBonzi
ID: 17151388
If you are resizing JPEGs or some other lossy format, then the reason you are seeing pixelation is because JPEGs don't handle resizing too well. When you take that extra step and copy the image to a new PSD, it's able to retain more information about the image during the resize than it would be able to with a JPEG.
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by:lherrou
ID: 17153030
>>> you are seeing pixelation is because JPEGs don't handle resizing too well.
>>> copy the image to a new PSD, it's able to retain more information about the image

I'm afraid that those combinations of statements are simply untrue.

GIF files do not handle re-sizing well, due to the reduced palette, which keeps the software from generating interim colors to soften linear edges, producing "jaggies". JPG handle resizing just fine. Perhaps you are confusing the other issue with JPG, which is that each time they are saved, additional information is lost in the compression process.


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by:YoungBonzi
ID: 17153473
Hmm...I thought the rule would apply to all lossy formats...
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by:cacklebunny
ID: 17157731
Let me clarify some points that were asked:

First, this issue is with DECREASING the size of images.

Second, the pixellation/distortion occurs whether I'm trying to resize a GIF, a JPG, a TIFF, a PNG file --it doesn't matter.  

Third, I have the magnification set to 100%, so the distortion I'm seeing is not the result of a magnification problem.

Lastly, someone asked me to look at the properties of the image and its color settings as it's opened in Photoshop. Let's take a PNG file as an example.  The PNG file I've opened has the following properties:

Indexed Color is checked
8-bit color is checked

In fact, any of the above image types I open in Photoshop will default to the above.

Thanks!
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by:cacklebunny
ID: 17172042
After I unchecked the default "Indexed Color" when I open a PNG file (or GIF, JPG, etc), switched it to RGB and then attempted to resize, all was well.

Now I'll need to figure out how to make it RGB by default!

Thanks for the help, lherrou!
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by:lherrou
ID: 17172100
Glad I could help! Thanks for the points and the "A".
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