Mailinglist Archive: opensuse (908 mails)

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Re: [opensuse] apache 2.4 performance issue / processwire.
On 2016-06-09 08:05, Per Jessen wrote:
Anton Aylward wrote:

On 06/08/2016 04:49 PM, Carlos E. R. wrote:
On 2016-06-08 21:03, Anton Aylward wrote:
On 06/08/2016 01:24 PM, Carlos E. R. wrote:
If you mean use a screen-scraper tool like KSnapshot then no
wonder you get poor quality!
no no. A screen capture is by definition "maximum quality"
always. It has a defined number of pixels, it is a memory image.
There is no possible error.

I disagree. It may well be that the image you are scraping from the
screen has a higher definition source. It may be that the original
source is a 2650x1800 image that has been rendered down to fit
256x174.

Why not wget the original?

Then it is not a screenshot.

Why is a screenshot so important?
To get on the screen it must have come from somewhere.
Why no make use of that original somewhere?

It depends on what you need it for. If you just like the background
image and want to use it on your desktop, copying the original
(Ctrl-I -> Media -> Save as) is the better option, but if you want to
document what it looked like on your screen, well ....

Notice that for me a screenshot is a screencapture, it is something for
which the original is the computer display, for whatever reason (think
of a page explaining how to use certain software). And as such, it has a
fixed number of pixels and colours. It can not be improved, it is what
it is (unless you switch the computer video hardware or choose another
possible resolution).

Then. Given a given picture, whatever source, it can be converted to
jpeg. Jpeg is a lossy format. It compresses at the cost of worse
quality. There is a compromise, you can improve the quality, or improve
the size, not both. Thus you can do several conversions at different
quality factors (from 1 to 100) and compare visually the results, and
choose which one you like. The compression itself can be done with
whatever software, but gimp has here a distinct advantage: it has a
slider to choose the quality, and as you move it you see the program
showing in a view how exactly will that picture display at the quality
you have just selected with the mouse. You move the slider to 99 and see
it perfect, and it tells you also what size you get. Too much, so you
decrease to 90. Very good, but I want smaller. Move the slider, watch
the image change the same instant and the size counter change, till you
hit the sweet point of size and quality, then save the picture at that
setting.

If you still don't understand what I mean, try it. You have to click on
the preview to display the target size for this to work. By default it
is disabled.

No other application does this with jpegs.

(I hate that cameras compress to jpeg. It should be png. At least a
choice. No, I do not know if Q=100 means no losses)


Try to compress a screenshot with text to jpeg. As you move the slider
to smaller size you will see the fonts to degrade a lot, get grainy,
undefined. Often it is not worth it and you have to select png or gif.

For the same size as jpeg, you can get much better results with "dejavu"
format. It is ideal for scanned text (which is why it is used by
libraries). Unfortunately, few programs support it. Not gimp. Nor
convert. If you are interested, I can explain more. There is a web site
with comparisons.




--
Cheers / Saludos,

Carlos E. R.
(from 13.1 x86_64 "Bottle" at Telcontar)

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