koobas.hobune.stream
SetPixels Not Transparent?
I am trying to use SetPixel with a brush image that has a round brush shape with a transparent background. The code is below. When I run this, the brush shape displays but with a white background. The output values for the first pixel are listed below, which should be transparent(?) since a=0.0, but it appears white when rendered. Or am I misunderstanding something?
function testAlpha(){ var tex=Instantiate(renderer.material.mainTexture); var pixels=brushTexture.GetPixels(0,0,brushTexture.width, brushTexture.height,0); var outputString=""; for (var y : int = 0; y < brushTexture.height; ++y) { for (var x : int = 0; x < brushTexture.width; ++x) { var brushColor=brushTexture.GetPixel(x,y); if(x==0){outputString+="brush color: "+brushColor+",";} if(x==0){outputString+="old text color: "+tex.GetPixel(x, y)+",";} tex.SetPixel (x, y, brushColor); if(x==0){outputString+="new tex color: "+tex.GetPixel(x, y)+"|";} } } Debug.Log(outputString); renderer.material.mainTexture=tex; tex.Apply(); }
brush color: RGBA(1.000, 1.000, 1.000, 0.000),old text color: RGBA(0.227, 0.459, 0.773, 1.000),new tex color: RGBA(1.000, 1.000, 1.000, 0.000)
Check this answer:
http://answers.unity3d.com/questions/43888/painting-stencil-on-a-surface
Here's the code I came up with that does this:
function compositeAlphaImage(baseImage, compositeImage, cx, cy){
// composite image with alpha channel onto base image
// cx and cy define the location of composite image relative to base image
var newImage=Instantiate(baseImage);
for (var y : int = 0; y < compositeImage.height; ++y) {
for (var x : int = 0; x < compositeImage.width; ++x) {
var compositeColor=compositeImage.GetPixel(x,y);
var baseColor=baseImage.GetPixel(cx+x, cy+y);
var alpha=compositeColor.a;
var newRed=(1-alpha)*baseColor.r+alpha*compositeColor.r;
var newGreen=(1-alpha)*baseColor.g+alpha*compositeColor.g;
var newBlue=(1-alpha)*baseColor.b+alpha*compositeColor.b;
var newAlpha=1.0;
var newColor=Color(newRed,newGreen,newBlue,newAlpha);
newImage.SetPixel (cx+x, cx+y, newColor);
}
}
return newImage;
}
I think there is a mistake here:
newImage.SetPixel (cx+x, cx+y, newColor);
it has to be
newImage.SetPixel (cx+x, cy+y, newColor);
Are you using a transparent shader to render with? Otherwise it'll disregard your texture's alpha.
I've tried both. Non-transparent shader results in a red circle with a white background (my brush) on a blue texture (my canvas). A transparent shader results in a red circle with transparency around the circle in the brush image area which shows transparency work. However, I'm trying to get a red circle on a blue background where the transparency applies when setting the pixel but not on the final texture.
Aah, I see, then $$anonymous$$ourosh's answer is probably what you want (blending between the colours), unless you just render an opaque blue plane behind it
