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I'm trying to save a jpg image but it's getting a bit blurred. I have it nicely in my image editor, but saving the image is not giving the quality I need, even with max quality defined.

If I save it as png, I get it with the sharpness I need.

Is there a way to overcome the loss of sharpness due to jpeg's compression? I really need it to be a jpg file.

You can check a sample of the image before and after here. As you can see, the orange is changing and the edges are not so sharp.

I start with a very high res jpg, change some colors, resize it, and save as jpg. If I save if first as png and then as jpg, still gets the same effect.

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What program are you using to export the file as .jpg? –  itsbc Mar 29 '12 at 21:19
    
Dante- Can you post samples of the images that are suffering from jpeg artifacts? Or maybe a screenshot containing both the pre-processed comp and the final output? –  Farray Mar 29 '12 at 23:42
    
I use Paint.Net. Screenshots posted. –  Dante Mar 30 '12 at 8:44
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Because the image is going to be the splashscreen of a windows phone application. Unfortunately, you cannot define your own image path, you have to use the existing one, which is a jpg. Stupid, imho, but I can't do anything about it. –  Dante Mar 30 '12 at 9:52
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@Dante: Ah, gotcha... I guess it can't be helped then, unless you've got a hex editor handy and can find where the image path is hardcoded. Though you might try just saving a PNG and naming it .jpg. This works in some cases. –  Lèse majesté Mar 30 '12 at 10:09
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3 Answers

up vote 1 down vote accepted

JPEG saves brightness (luminance) and color (chrominance) of the image in separate channels.

And JPEG has an option (used in your case) to save chrominance at half of resolution, since human eye is generally much less sensitive to changes of color hue than brightness.

So what you're seeing is "4:2:2" type of JPEG. To get perfectly sharp edges you need "4:4:4" JPEG that saves chrominance at full resolution.

Some programs automatically choose "4:4:4" variant when you set quality to more than 75%, so try exporting JPEG from a different program.

OR use PNG format, which preserves hard edges and will generally work better for such image with flat areas.

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Thanks for all you new contributions porneL! –  Yisela Mar 5 '13 at 21:50
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JPG is a lossy scheme. There will always be image degradation when saving as a jpg. If you started with a jpg, then save to a jpg things get even worse, fast.

If a jpg set on maximum quality is not yielding the results you wish, then chances are there is no solution other than to live with the quality you are getting if the image must be a jpg.

You might try saving as the png (which you state looks good) then open the PNG and save that as a jpg at max quality - might work... might not.

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Tried saving as png first, didn't do the trick. But thank you for the idea. –  Dante Mar 30 '12 at 8:44
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I'm not familiar with paint.net specifically, but if you see a sharp image in the editor and it's blurry after export then it is being blurred by the program, not compression. Compression doesn't create blur, but one of the ways that a program can improve the jpeg compression ratio of an image is to give it a slight blur. In Photoshop, for example, there is a blur setting for this purpose in the jpeg "Save for Web" dialog. If you look around in the paint.net export dialog, I'm guessing there will be a blur setting you overlooked earlier.

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No, I can't set the blur in paint.net. I'll check Photoshop. Thanks for the input ;) –  Dante Mar 30 '12 at 8:45
    
Does it appear blurry when opened in Chrome (file://image.jpg) It could be just the paint.net preview environment that blurs it. If all fails press PrintScrn, paste it in Paint.exe and save as jpg from there ^_^ –  Miro Mar 31 '12 at 2:37
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