# Any way to write to just the R, G, or B channel of the canvas? blendMode(ADD) is not working as expected

**URL:** <https://discourse.processing.org/t/any-way-to-write-to-just-the-r-g-or-b-channel-of-the-canvas-blendmode-add-is-not-working-as-expected/23347>\
**Category:** Coding Questions\
**Created:** [August 19, 2020, 2:40am UTC](https://discourse.processing.org/t/any-way-to-write-to-just-the-r-g-or-b-channel-of-the-canvas-blendmode-add-is-not-working-as-expected/23347 "2020-08-19T02:40:32Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![neel](https://avatars.discourse-cdn.com/v4/letter/n/f475e1/32.png) [@neel](https://discourse.processing.org/u/neel)\
**Post date:** [August 20, 2020, 12:11pm UTC](https://discourse.processing.org/t/any-way-to-write-to-just-the-r-g-or-b-channel-of-the-canvas-blendmode-add-is-not-working-as-expected/23347/6 "2020-08-20T12:11:32Z")

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Wow. That made a substantial difference.

I actually made another post about this, in the hopes that it would be more identifiable for future searchers. Hopefully that wasn’t poor form for this forum.

> [@Slow performance when passing multiple PGraphics into each other as shader textures](https://discourse.processing.org/t/slow-performance-when-passing-multiple-pgraphics-into-each-other-as-shader-textures/23384):
>
> Hey all, I’m attempting to use multiple pgraphics objects for my code. I want to draw some shapes on the first pgraphics. I then want to use a shader on the second pgraphics object to apply blur to the red channel and to generate a feedback loop by saving the previous version of this pgraphics and feeding it in as a texture. Finally, I want to feed the output of the second pgraphics into the third pgraphics so that I can apply some color transformations. This process seems to be tanking my fra…

I’ll post an update there and credit you. Thank you again!

In my actual code (not simple enough to post), I use get() in order to save the previous image for one of my PGraphics objects and feed it back into itself for feedback. Is there some way to do that without calling get()?

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