I don't believe so. Can you tell if the pixels are more than one off in any channel? That might be acceptable tolerance.
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quality loss in IrfanView's lossless conversions?
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Yes, a lot of pixels. I pick a random sample from the middle of the image.
Ulead Photo Explorer: RGB=(40,9,29)
all other programs*: RGB=(42,10,33)
*all other programs=all except Photoshop+Elements=IrfanView, XnView, ImageMagick, media-convert.com, MS Paint, ACDSee, FastStone MaxView
Don't bother with it. Maybe something in the "preferences" or "color settings" ...
BTW, what version of Photoshop Elements do you use ? And as I'm sure that Photoshop Elements supports color management, what are your settings there for the RGB working color space ?Last edited by boarder's paradise; 05.12.2008, 10:58 PM.
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Sorry, I slip out of here now and again. I got your message.
Originally posted by boarder's paradise View PostYes, a lot of pixels. I pick a random sample from the middle of the image.
Ulead Photo Explorer: RGB=(40,9,29)
all other programs*: RGB=(42,10,33)
Don't bother with it. Maybe something in the "preferences" or "color settings" ...
BTW, what version of Photoshop Elements do you use ? And as I'm sure that Photoshop Elements supports color management, what are your settings there for the RGB working color space ?
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thanks for the additional images. You have quite some apps
He,he, ... yes you are right PhotoStudio is way off and PictureGear generates exactly the same image as IrfanView and all the other apps. Now I am curious ... how did you know ??
Anyway, I'm happy ... the list of applications I can throw at them @Adobeforums grows and grows ....
That's what I call teamwork in times of web2.0Last edited by boarder's paradise; 06.12.2008, 02:41 AM.
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Only a handful of what I have...
I looked at the same three pixels as before and figured so.
It's possible that most applictions use the same popular codec, but maybe the others are using a variation that is also possibly better quality. If you can't tell out of 16.7 million colors which one is better, then why worry?
I feel for your curiosity, as I have curiosities, too. However. considering the time you are willing to devote to this, over that of whatever this is intended for, you could probably learn the standard and figure out why this is happening. But, most people don't wish to; they just accept or trust the technology. Most people would rather spend their time being one of the people in the image.
Like others have said, jpg is lossy at any compression level, so why should decompression be perfect? If one is willing to use jpg at all, quality surely cannot be a factor in their work, as jpg is not synonamous with quality at all. You don't seem to question why jpg is used so prevalently, which I think is a far worse problem.
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Originally posted by Skippybox View PostOnly a handful of what I have...
Most people would rather spend their time being one of the people in the image.
Like others have said, jpg is lossy at any compression level, so why should decompression be perfect?
If one is willing to use jpg at all, quality surely cannot be a factor in their work, as jpg is not synonamous with quality at all.
You don't seem to question why jpg is used so prevalently, which I think is a far worse problem.
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Yes, it is the original PhotoShop Elements. It came preinstalled on my notebook, which is 7 years old. I saw no reason to upgrade, since I don't use it too much and there are free software titles that do about the same things. Maybe I'll upgrade someday, huh?!
I keep many thing a while, as there really isn't a reason to pay for a few features in an upgrade. Besides, it runs fine being small. I couldn't run 7 if I wanted to anyway!Last edited by Skippybox; 09.12.2008, 10:26 PM.
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The differences are related to dct method and fancy upsampling.
The Discrete Cosine Transform (DCT) method works with blocks of 8x8 pixels and all those calculations by approximation affects visual representation.
Here is part of a header file
Code:typedef enum { JDCT_ISLOW, /* slow but accurate integer algorithm */ JDCT_IFAST, /* faster, less accurate integer method */ JDCT_FLOAT /* floating-point: accurate, fast on fast HW */ } J_DCT_METHOD;
The JPEG default colorspace is YCbCr.
The components are downsampled during compression by the chroma factors and later upsampled during decompression.
This upsampling is handled differently by different programs.
Fancy upsampling is a option of IJG library to better approximate the original component values. I don't know what Photoshop is using but I heard it simply uses a fast method.
The original IJG library uses also some kind of resampling methods for approximation like nearest neighbor (box, pixel replication),
or bilinear interpolation (triangle). They can introduce pixelation or blurring.
The IJG code is very technical and it takes someone with strong mathematical and programming knowledge to understand it. Also you need to understand first the JPEG papers. i don't know exactly what JPEG does internally to explain more than I did.RIOT developer
visit the Radical Image Optimization Tool website
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Thanks so much for your insights, Lucian.
I had asked the question at the official Adobe forum, too. Noone was able to give a technical comment like you do. You would be deerly welcomed over there, if you want:
Quite a few of them are really talking nonsense and I feel you would be easily competent enough to expose that.
But anyway, thanks a lot, your informations made me understand the whole thing a lot better.
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Originally posted by boarder's paradise View PostI thought jpeg-encoding is lossy, jpeg-decoding is lossless. People over there at adobeforums.com have different opinions about it.
What do you use? RAW and lossless jp2 ?
I try to use PNG, BMP, and TIF for some things. I wouldn't pay for a JP2 license. Most cameras have stopped supporting BMP and so JPG reigns. RAW isn't really a format, takes too much resources/time to fiddle with, and many times is lossy compressed anyhow. So for cameras, JPG is what I use. The best you can do is have a high quality camera, but mine can't shoot RAW.
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