This is my first post on this forum and sure not the last one. I hope to contribute to the forum soon.

I got a question about blend() in combination with rotated images. I wrote this script but i am yet unable to multiply different images rotated and stacked upon each other. Also i'd like to multiply these images with the background, and at a later time with other circles on top.

Is it even possible to rotate a blend ?
And is this the right way to accomplish this ?

Thanks in advance.

Code:

PImage b;

// Radius/Shape nitialization
float xCenter = 350;
float yCenter = 350;
float radius = 100;

float xOffset = -20;
float yOffset = -60;

float nrSteps = 10;
float degreeValue = 0;

float circleX;
float circleY;


void setup() {
  size(700, 700);
  background(255);
  b = loadImage("http://www.muhneer.nl/files/preview/fff_pic.jpg");
  noLoop();
}

void draw() {
  println(nrSteps);
  drawCircle();
}

void drawCircle() {
  for (int i = 1; i <= nrSteps; i = i+1) {
    degreeValue = 360/nrSteps;
    circleX = round(xCenter + (cos(radians(degreeValue*i))*radius));
    circleY = round(yCenter + (sin(radians(degreeValue*i))*radius));
    item(circleX, circleY, degreeValue*i);	
  }
}

void item(float x, float y, float angle) {
  pushMatrix();
  translate(x, y);
  rotate(radians(angle));
  //b.blend(b, 0, 0, 76, 76, 10, 10, 76, 76, MULTIPLY);
  image(b, xOffset, yOffset);
  //rect(0, 0, 150, 120);
  //blend(b, 0, 0, 150, 120, 10, 10, 150, 120, MULTIPLY);
  point(0, 0);
  popMatrix();
}
 

i've used this, and it works well

it get's rid of the black line and it does the same thing as filter(MULTIPLY), with the images overlapping.

Code:

//--------------------------------------------------------------
//opengl
//--------------------------------------------------------------
pgl.beginGL();
gl.glEnable(GL.GL_TEXTURE_2D);

//blending function
gl.glEnable(GL.GL_BLEND);
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);

// Texture
tex.bind();
tex.enable();

//image coordinates
gl.glBegin(GL.GL_QUADS);
gl.glNormal3f(0.0f, 0.0f, 1.0f);
gl.glTexCoord2f(0, 0); gl.glVertex2f(0, bild[w].height);
gl.glTexCoord2f(1, 0); gl.glVertex2f(bild[w].width, bild[w].height);
gl.glTexCoord2f(1, 1); gl.glVertex2f(bild[w].width, 0);
gl.glTexCoord2f(0, 1); gl.glVertex2f(0, 0);
gl.glEnd();

tex.disable();
gl.glDisable( GL.GL_BLEND );

pgl.endGL();
 

however, i want to output graphics with an alpha channel, and it seems that PGraphics http://processing.org/reference/createGraphics_.html doesn't work with openGL "It's not possible to use createGraphics() with OPENGL..."

is there another solution to have a "multiply" effect on rotated images, that doesn't involve openGL

any help would be much appreciated.

thanks.
Ken