[Newbies] Reading PNG images into squeak image is slow
leves at elte.hu
Tue Oct 22 23:14:15 UTC 2013
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,
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
>>> (PNGReadWriter formFromFileNamed: something) durationToRun
>>> "unacceptale if you want to program an image browser"
>>> 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.
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