On Wed, 23 Oct 2013, Ben Coman wrote:
Levente Uzonyi wrote:
On Tue, 22 Oct 2013, Mateusz Grotek wrote:
It is (even on Cog).
What is the reason for that?
Is it a problem with the algorithm used in the image or it's unsolvable
inside the image and a plugin or FFI is needed.
I doubt it can be significantly faster using smalltalk only. When we wanted
to store images in files using lossless compression, we decided to use jpeg
instead of png, because it has plugin support, so it's a lot faster to load
and save the images.
That sounds contradictory since JPEG is not lossless (I know you know, just
stating the obvious). For computer generated images with solid blocks of
colour JPEG can have artifacts. PNG is lossless. In general, photo=JPEG,
graphics=PNG.
You have to set the quality parameter to 100 to get a lossless image. The
only drawback versus png is that it only supports three channels, so there
will be no alpha channel in those images. But that was not a problem for
us.
Levente
P.S.
Code:
(PNGReadWriter formFromFileNamed: something) durationToRun
"0:00:01:09.591"
"unacceptale if you want to program an image browser"
Data:
1301.png: PNG image data, 2048 x 1536, 8-bit/color RGB, non-interlaced
(a pic of a street taken from a cell phone)
That image is huge. Cell phones and digital cameras usually create jpeg
images. But if you really need to support png, then ffi or a plugin is the
way to go.
I believe this is because a higher level of compression would take longer and
use more battery. You can use http://www.xnview.com/
to often drop 80% of the file size of of cell phone images without any
apparent loss of quality.
If that is a concern, then I'm pretty sure these machines have hardware
which can compress the images. The do have it for video (mpeg2/h264), so
adding jpeg is basically no extra cost.
On the other hand, I don't think creating a png file is computationally
less expensive, than creating a jpeg file.
Levente
-ben
Levente
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