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Author Topic: Poor picture quality - Why?  (Read 1820 times)

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McKenzie

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Poor picture quality - Why?
« on: September 01, 2008, 03:49:29 pm »

Hello,

my pictures have not such a good definition like pictures on Wikipedia and so on, but my pictures have a larger size. The pictures look a bit softer and unsharp.

I use GD2
Quality for JPEG files: 94
Auto resize images that are larger than max width or height : Yes:Everyone
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McKenzie

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Re: Poor picture quality - Why?
« Reply #1 on: September 01, 2008, 03:54:53 pm »

By the way I used that picture as original (Picture is under public domain, so it is okay that I use it here).

I resized original pictures to 1200x....
I resized displayimage pictures to 808 x....
I resized thumbnail pictures to 150 x....
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apanda

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Re: Poor picture quality - Why?
« Reply #2 on: September 02, 2008, 03:04:51 am »

A couple of things are happening to your images.

1.  Jpegs are a lossy image format.  That allows strong file compression but it also means that means that every time a picture is converted into a new jpeg image, some information is lost.  Pictures get less and less sharp every time they are changed (unless you save at 100% for your jpegs, and then your files are huge).

2.  Changing the size of an image also makes the image fuzzier.  For example, if you scale 2 pixels into 1, the color of the 1 will probably be the average of the 2.  If you then double the size back, there is no way for the enlarging program to know what the 2 original colors were so you just get more of the average color.

Changing the size of your images so often is why you are losing quality.

One thing you could do is let Coppermine generate the mid-size image then replace it with the original, which will still have its original quality.
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