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  [LibGDX] Make Texture/Sprite black and white?  (Read 1491 times)
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Offline Slyntax

Junior Member


Medals: 3



« Posted 2013-03-22 07:53:10 »

Is there any way to remove the color from a Texture in LibGDX and be left with a grayscaled image?
Offline davedes
« Reply #1 - Posted 2013-03-22 08:07:13 »

If you don't need it done in real-time, then you're better off using Photoshop or GIMP to save two copies of your image.

If you need it in real-time or need to process a lot of sprites, using shaders is the ideal solution.

Shader Lesson 3: Grayscale and other effects
Code example

Another solution is to process the Pixmap before uploading it to a Texture:
Pixmaps & Textures

Offline Slyntax

Junior Member


Medals: 3



« Reply #2 - Posted 2013-03-22 08:16:13 »

Yeah looking through the LWJGL Shader Tutorial now and that looks like the better solution.

Thanks a million for the code example as well. That will save me a ton of time lol.
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Offline relminator
« Reply #3 - Posted 2013-03-22 08:23:18 »

Depending on what version of GL you're using you can use glTexEnvf() + glTexEnvfv() + glColor() to draw pure white sprites. Or its shader counterpart.
Offline Slyntax

Junior Member


Medals: 3



« Reply #4 - Posted 2013-03-22 09:00:05 »

If you don't need it done in real-time, then you're better off using Photoshop or GIMP to save two copies of your image.

If you need it in real-time or need to process a lot of sprites, using shaders is the ideal solution.

Shader Lesson 3: Grayscale and other effects
Code example

Another solution is to process the Pixmap before uploading it to a Texture:
Pixmaps & Textures

Yeah it needs to be done in real time. So I'm going with Shaders. I found settings for a default shader as well.

My problem right now is that when I apply the grayscaled shader nothing renders... but when I set the shader to the default it renders everything after it fine.

I'm, obviously, very new to shaders so is there anything simple that I might be missing?

Note: I copied VERT and FRAG entirely from the code example.

This is what takes place in my render...

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batch.setShader(shader);
time += Gdx.graphics.getDeltaTime();          
grayscale = (float)Math.sin(time)/2f+0.5f;
       
shader.begin();
shader.setUniformf("grayscale", grayscale);
shader.end();

sprite.draw(batch);
batch.setShader(default_shader)
...
Offline Slyntax

Junior Member


Medals: 3



« Reply #5 - Posted 2013-03-22 09:36:52 »

Figured it out.

Didn't need to use

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time += Gdx.graphics.getDeltaTime();           
grayscale = (float)Math.sin(time)/2f+0.5f;
       
shader.begin();
shader.setUniformf("grayscale", grayscale);
shader.end();


It's now just...

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batch.setShader(shader);
sprite.draw(batch);
batch.setShader(default_shader)


And works as expected.
Offline davedes
« Reply #6 - Posted 2013-03-22 18:02:27 »

The "grayscale" uniform allows you to change the strength of the effect; i.e. in case you want some things grayscale and some things in color.

Read through lessons 1 - 3 for more info on using uniforms.

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//start rendering your batch
batch.begin();

//enable grayscale
shader.setUniformf("grayscale", 1.0f);

//draw your grayscale entities
for (...)
   batch.draw(...);

//now FLUSH the batch; same as using end() + begin()
batch.flush();

//now disable the grayscale effect
shader.setUniformf("grayscale", 0.0f);

//... render your color entities ...//

//finish rendering
shader.end();


This only affects the proceeding batch. So your code needs to look like this:

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