21 Sep
2010
21 Sep
'10
7:58 p.m.
Hi Sergiu,
On 09/21/2010 08:27 PM, Sergiu Dumitriu wrote:
On 09/08/2010 10:40 PM, Marius Dumitru Florea wrote:
The default compression quality is configurable. The question is what do
we favor by default: performance or quality?
Hi devs,
Currently the image plugin [1] allows us to create image thumbnails by
specifying the image width and/or height in the query string of the
image attachment download URL:
/xwiki/bin/download/Spage/Page/image.jpg?width=100
I propose that we:
(A) Use the image width and/or height (when they are specified in the
image syntax using pixel unit) to resize the image on the server side.
For instance:
[[image:logo.jpg||width="100px"]]
will be linked to
/xwiki/bin/download/Spage/Page/logo.jpg?width=100
and
[[image:logo.jpg||style="height: 50px; width: 70px"]]
will be linked to
/xwiki/bin/download/Spage/Page/logo.jpg?width=70&height=50
+1.
The image plugin also accepts a quality parameter
that controls the
compression quality when encoding jpeg images. The default value of this
parameter (i.e. when not specified in the URL) is configurable. I
propose we use 0.3 by default, 1 representing the best quality.
0.3 seems very low to me. The resulting image has serious artifacts,
which can be ignored for low-level photographs, but which is
unacceptable if the images are technical. I think that we should try to
give less artifacts.
One option would be to use the same quality as the original image, but I
don't know if the JDK has APIs for reading this information from the
picture, although it can be obtained by parsing the raw image. The
simpler thing would be to use something in the middle, 0.5? (B) Add the ability to limit the image dimensions
(preserving aspect
ratio) when the image width and/or height are not specified in the image
syntax (or when they are not using pixel unit). The width and height
limit will be configurable and -1 by default (i.e. no limitation). For
instance:
image:logo.jpg
will be linked to
/xwiki/bin/download/Spage/Page/logo.jpg?width=1024
when width limit is 1024, and to
/xwiki/bin/download/Spage/Page/logo.jpg?width=1024&height=768&keepAspectRatio=true
when width limit is 1024 and height limit is 768. Note that in this case
the image aspect ratio is preserved. The image is resized to best fit
the limits. If the user want to bypass the limit he has to specify the
image width/height in the image syntax.
I'm not sure of this. How do you get the original
image back?
Either you set the width/height limit to -1 or to a reasonable large
number in the configuration or you specify the original image
width/height in the image wiki syntax. Alternatively you can create a
link to the original image with:
[[image:logo.jpg>>attach:logo.jpg]]
Note that image width/height limit are -1 by default in the standard XE
distribution. Their purpose it to limit image width/height in wikis
where users upload large images that can't be display in their full size
on a web page (e.g. 3648 x 2736 px). In this case a link to the original
image is enough.
Thanks for the feedback,
Marius
I'm +1 for both (A) and (B). WDYT?
Thanks,
Marius
[1]
http://svn.xwiki.org/svnroot/xwiki/platform/core/trunk/xwiki-core/src/main/…