[Newbies] Reading PNG images into squeak image is slow

[Levente Uzonyi]

On Wed, 23 Oct 2013, Ben Coman wrote:

> Levente Uzonyi wrote:
>> 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.
>
> Thats interesting. I'd never heard of that.  I always believed 100 was still 
> lossless per [1] [2].  What software did you use for the lossless JPEG 
> encoding? cheers -ben
>
> [1] 
> http://stackoverflow.com/questions/7982409/is-jpeg-lossless-when-quality-is-set-to-100
> [2] 
> http://photo.stackexchange.com/questions/19876/converting-raw-images-to-lossless-jpeg-using-gimp

You're right, it's not lossless, but the difference is not visible by a 
human on non-forged images.


Levente

>
>> 
>> 
>> 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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