[etoys-dev] How can I access the individual pixels in an image

[Steve Thomas]

[image: Inline image 1]

Thanks!!!

So that explains why the red, green, blue values go 0 to 100 instead of 0
to 255.

The kids will have fun with this, I am going to try and get them to create
some "green screen effects" using Etoys.  I'll let everyone know how it
goes and post a how on the squeakland list.

Stpehen

On Fri, May 25, 2012 at 2:32 PM, Bert Freudenberg <bert at freudenbergs.de>wrote:

> Well, for one, all these values are fractions in the range 0 to 1.
>
> If you use 0 in your example, the image will become fully transparent. If
> you use 1, it will be fully opaque.
>
> Since 16 bit forms store only 1 bit of alpha (and 5 bits each for red,
> green, and blue), you cannot do more than toggle that bit.
>
> If you want real translucency, create newForm with 32 bits of depth
> instead of 16. Then each component gets full 8 bits, and e.g. using an
> alpha of 0.5 will make the whole image half-transparent.
>
> - Bert -
>
> On 25.05.2012, at 20:23, Steve Thomas wrote:
>
> <Screen Shot 2012-05-25 at 2.22.06 PM.png>
> I tried setting alpha to 50, but it didn't work, see script below.
>
> recolor
> | oldForm newForm old new avg |
> oldForm := ErnieRubberDuckie getGraphic.
>  newForm := Form extent: oldForm extent depth: 16.
> 0
> to: oldForm height - 1
>  do: [:y | 0
> to: oldForm width - 1
> do: [:x |
>  old := oldForm colorAt: x @ y.
> avg := old red + old green + old blue / 3.
>  new := Color
> r: old red * 0 + avg
> g: old green * 0 + avg
>  b: old blue * 0 + avg
> * alpha: 50.*
> newForm colorAt: x @ y put: new]].
>  self setGraphic: newForm
>
>
>
>> On Fri, May 25, 2012 at 7:59 AM, Bert Freudenberg <bert at freudenbergs.de>wrote:
>>
>>> On 25.05.2012, at 12:35, Steve Thomas wrote:
>>>
>>> How can I loop through each pixel in an image and get their
>>> red,green,blue values?
>>> I also would like to be able to create a new image using those values
>>> (modified, for example set red=red*0.5)
>>>
>>> I know Karl did a great project Color Reading And Writing<http://www.squeakland.org/showcase/project.jsp?id=7044> which
>>> I could use, but would like to introduce some of the kids to squeak.
>>>
>>>
>>> <PastedGraphic-10.png>
>>>
>>> <PastedGraphic-11.png>
>>>
>>> - Bert -
>>>
>>>
>>
>
>
>
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