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Index › Programming Questions & Help › Syntax Questions › PGraphics Alpha issue
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PGraphics Alpha issue (Read 676 times)
nospec
PGraphics Alpha issue
Jun 15th, 2007, 2:30pm  
I am trying to use a PGraphics object as a texture but i would like it to be semi transparant...
I don't seem to be able to resolve the problem, even after searching the forum... If anyone could tell me what i'm doing wrong i would be very grateful!!!

Here's an example of my code...

PGraphics myTexture;

void setup()
{
 frameRate(1);
 size(320,240);
 background(255);
 myTexture = createGraphics(160,120,JAVA2D);
}
 
void draw()
{
   
   myTexture.beginDraw();
   myTexture.background(255,0,0);
   myTexture.ellipse(80,60,10,10);
   myTexture.endDraw();
   myTexture.modified = true;
   
   myTexture.loadPixels();
   for (int i = 0; i < myTexture.width * myTexture.height; i++)
   {
     float r = red(color(myTexture.pixels[i]));
     float g = green(color(myTexture.pixels[i]));
     float b = blue(color(myTexture.pixels[i]));
     myTexture.pixels[i] = color(r, g, b,128);
   }
   myTexture.updatePixels();
   
   image(myTexture,20,20);
}
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davbol
Re: PGraphics Alpha issue
Reply #1 - Jun 15th, 2007, 6:53pm  
Your code is actually working, but because you're not clearing the background on each frame your transparent images are accumulating and quickly appear opaque.  To fix that just add a call to background() at the top of draw().

Also, just a tip, you can use tint() to set transparency instead of manipulating the pixels yourself:

Quote:

void draw()
{
   background(255);
   myTexture.beginDraw();
   myTexture.background(255,0,0);
   myTexture.ellipse(80,60,10,10);
   myTexture.endDraw();
   myTexture.modified = true;
   tint(255,128);
   image(myTexture,20,20);
}
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WWW  
nospec
Re: PGraphics Alpha issue
Reply #2 - Jun 15th, 2007, 8:43pm  
Thank you Dave for your quick response... What a stupid mistake to make, but i just didn't see it.
About the tint() function. If I want to apply the texture to a shape, i don't immediately see a way to implicate it. The alpha thing (though not through bitwise operations, i'm not that comfortable using bit things) seems to work.
Thanx again!!!

PGraphics myTexture;

void setup()
{
 frameRate(1);
 size(320,240,P3D);
 background(255);
 myTexture = createGraphics(160,120,JAVA2D);
}

void draw()  
{  
   background(255);
   myTexture.beginDraw();  
   myTexture.background(255,0,0);  
   myTexture.ellipse(80,60,10,10);  
   myTexture.endDraw();  
   myTexture.modified = true;
   
   myTexture.loadPixels();
   for (int i = 0; i < myTexture.width * myTexture.height; i++)
   {
     float r = red(color(myTexture.pixels[i]));
     float g = green(color(myTexture.pixels[i]));
     float b = blue(color(myTexture.pixels[i]));
     myTexture.pixels[i] = color(r, g, b,128);
   }
   myTexture.updatePixels();
   
   image(myTexture,20,20);
   
   beginShape();
   texture(myTexture);
   vertex(10,10,0,0);
   vertex(100,10,160,0);
   vertex(100,120,160,120);
   vertex(10,120,0,120);
   endShape();
   
}
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