Thijs Koerselman

When using "copypixels" I always have to disable blending beforehand,

because otherwise the copied pixels are blending with the glclearcolor.

Patterns can be another sketch instance or an Image. Same problem. Is this

expected behavior or a bug maybe? I know this isn't a proper bugreport so if

it's not something I'm missing I'll make an example script.

When using "copypixels" I always have to disable blending beforehand,
because otherwise the copied pixels are blending with the glclearcolor.

draw()
{
   sketch.glclear();
   sketch.gldisable("blend");
   sketch.copypixels(Patterns, 0, 0);

Patterns can be another sketch instance or an Image. Same problem. Is this
expected behavior or a bug maybe? I know this isn't a proper bugreport so if
it's not something I'm missing I'll make an example script.

copypixels-blending-bug

On Jul 31, 2006, at 7:35 AM, Thijs Koerselman wrote:

> When using "copypixels" I always have to disable blending 

> beforehand, because otherwise the copied pixels are blending with 

> Patterns can be another sketch instance or an Image. Same problem. 

> Is this expected behavior or a bug maybe?

This isn't a bug, but rather a feature. When blending is enabled we 

respect the alpha channel of the source image, or if the source is an 

instance of sketch, an alpha channel with the alpha value of the 

> When using "copypixels" I always have to disable blending  
> beforehand, because otherwise the copied pixels are blending with  
> the glclearcolor.
>
> draw()
> {
>    sketch.glclear();
>    sketch.gldisable("blend");
>    sketch.copypixels(Patterns, 0, 0);
>
>    refresh();
> }
>
> Patterns can be another sketch instance or an Image. Same problem.  
> Is this expected behavior or a bug maybe?

This isn't a bug, but rather a feature. When blending is enabled we  
respect the alpha channel of the source image, or if the source is an  
instance of sketch, an alpha channel with the alpha value of the  
current draw color is used.

Ah I see, it was glcolor then. I was already getting strange behavior with

the alpha of some content depending on the drawing of other things, and this

explains all. Thanks for clearing this up, I should have checked the manual

> This isn't a bug, but rather a feature. When blending is enabled we

> respect the alpha channel of the source image, or if the source is an

> instance of sketch, an alpha channel with the alpha value of the

Ah I see, it was glcolor then. I was already getting strange behavior with
the alpha of some content depending on the drawing of other things, and this
explains all. Thanks for clearing this up, I should have checked the manual
about copypixels cause its all in there.

On 7/31/06, Joshua Kit Clayton  wrote:
>
>
>
> This isn't a bug, but rather a feature. When blending is enabled we
> respect the alpha channel of the source image, or if the source is an
> instance of sketch, an alpha channel with the alpha value of the
> current draw color is used.
>
> -Joshua
>
>


copypixels blending bug?