[Etoys] alpha property

[Bert Freudenberg]

On 25.04.2009, at 09:38, Karl Ramberg wrote:

> On 2009-04-24 23:13, Jerome Peace wrote:
>>
>> Hi Karl,
>>
>> --- On Fri, 4/24/09, Karl Ramberg <karlramberg at gmail.com> wrote:
>>
>>
>>> From: Karl Ramberg <karlramberg at gmail.com>
>>> Subject: Re: [Etoys] alpha property
>>>
>>
>>> I think this would be a nice addition to the Etoys image as
>>> well, with some needed integration with Etoys.
>>>
>> It is the etoy integration that is the problem.
>>
>> Look at how etoys handles things.
>>
>> Etoys has hobbled itself to avoid some bugs with translucency.
>> First it comes up default with a 16 bit display.
>> At that depth no translucency can be shown.
>> Switching to 32 bit depth can correct that.
>>
>> But it doesn't help.
>> Sketch morphs have slots for the original form.
>> and a rotated form.
>> The last is the original form processed by the rotation/stretching/ 
>> scaling that has be done to the sketch by the handles.
>> It is the rotated form that actually gets displayed.
>> In the processing the form is forced to be depth 16.
>> So you will never see translucent sketches
>> even if the base graphic and original form are translucent.
>> This is what stumped me.
>>
>> Work arounds are hard to come by.
>> An ImageMorph is the other way to hold a form for display.
>> It was designed to be simple and does not allow direct scaling.
>> Etoys makes it very hard to get an ImageMorph and has no natural  
>> way for putting an image into one.
>>
>> That leaves putting an image in a BitmapFill.
>> This might work but not from tiles.
>>
>> And it is questionable to put time into development
>> when the mindset is hide faults by hobbling the languages abilities.
>>
>> As you might be hearing from my tone, I am somewhat disappointed.
>>
>> Yours in curiosity and service, --Jerome Peace
>>
>
> Uh, I did not know this...
> Well, I guess it should be posted as a bug/enhancement project on  
> the bug tracker.


It's a trade-off. At 16 bpp we have to shove around only have as much  
data as in 32 bpp. Our painting tools do not support alpha  
transparency. If you use translucency and gradients, powerful tiles  
like color-sees do not work as well. That's also the reason why we  
don't smooth rotated sketches, because it alters the colors.

Now that said, we actually do support alpha transparency in 16 bpp.  
You can take an ellipse and set its alpha to 50 and it works. One  
could do the same for images. Perhaps even more powerful would be a  
special kind of holder that would adjust all its childrens'  
transparency. That way, any object could be made translucent by  
embedding.

- Bert -


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