Linked by Andrew Youll on Wed 27th Jul 2005 16:58 UTC, submitted by Qwerty
Windows Microsoft has released some official screenshots of the just released beta 1 of Windows Vista, their upcoming Windows version. Microsoft has passed a major milestone with the release of its first full test version of Windows Vista, the next generation of its flagship operating system.
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RE: 1MiB+ jpeg?
by on Wed 27th Jul 2005 18:36 UTC in reply to "1MiB+ jpeg?"

Member since:

When I save the 1,5MB JPG as PNG it gets 2,6MB big, not really an improvement. Also IE has only problems with transparency in PNGs, not something you would need for screenshots.

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RE[2]: 1MiB+ jpeg?
by evert on Wed 27th Jul 2005 18:43 in reply to "RE: 1MiB+ jpeg?"
evert Member since:
2005-07-06

PNG is a losless format, JPEG is not. that's why PNG's are bigger. But maybe you want to check the PNG compression rate, not all apps compress the PNG file to the optimum...

Screenshots, IE, and transparany are no problem at all because screenshots should not use transparancy. Anyway, IE only has transparancy problems if you use multiple alpha channels for your PNG file.

Microsoft just doesn't like PNG that much, on the other hand: you can store PNG files from MS Paint.

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RE[3]: 1MiB+ jpeg?
by on Wed 27th Jul 2005 19:09 in reply to "RE[2]: 1MiB+ jpeg?"
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Evert:
Hmm, somehow you tried to correct my points by stating them again.
The original poster was whining about 1,5MB JPEGs, so I pointed out that a lossless PNG would be even bigger. If what the poster really wanted was a lossless image, well PNG is not the only format for that, a BMP or TIFF would do just as well.

Then he ranted on about PNG support in IE, but the only issues are related to transparency, nothing of relevance for screenshots.

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RE[2]: 1MiB+ jpeg? - Public info broadcast
by Phil on Wed 27th Jul 2005 20:18 in reply to "RE: 1MiB+ jpeg?"
Phil Member since:
2005-07-06

Lossless compression is very differently grounded to lossy compression.

In short, jpeg adds rubbish to an image to fill up the spaces. When you then make a png version, you save all that rubbish, pixel for pixel, which takes a lot of memory. If you went straight to png on the other hand, you would simply save the fact that there was an empty space at a particular point.

Obviously, this is exactly true, but I think it gets the point across.

Reply Parent Score: 1

Member since:

Phil:
In short, jpeg adds rubbish to an image to fill up the spaces. When you then make a png version, you save all that rubbish, pixel for pixel, which takes a lot of memory. If you went straight to png on the other hand, you would simply save the fact that there was an empty space at a particular point.

Me:
Sure, if we were talking about a screenshot of, say DOS. In this case going from lossy to lossless wound preserve the boundary-artefacts and increase the size of the PNG.
But the screenshots in question contain a photographic wallpaper and lots of gradients which will result in poor compression in most lossless formats. Some jpeg-“rubbish” will make no significant difference.

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