pixelWidth

When pixelDensity(2) is used to make use of a high resolution display (called a Retina display on OS X or high-dpi on Windows and Linux), the width and height of the sketch do not change, but the number of pixels is doubled. As a result, all operations that use pixels (like loadPixels(), get(), set(), etc.) happen in this doubled space. As a convenience, the variables pixelWidth and pixelHeight hold the actual width and height of the sketch in pixels. This is useful for any sketch that uses the pixels[] array, for instance, because the number of elements in the array will be pixelWidth*pixelHeight, not width*height.

• void setup() {
   size(600, 400);
   pixelDensity(2);
   println(width, height);
   println(pixelWidth, pixelHeight);
  }
  

• void setup() {
   size(600, 400);
   pixelDensity(2); // Double the pixel density
   println(width, height);
   println(pixelWidth, pixelHeight);
  }
  
  void draw() {
   loadPixels();
   // Fill all the pixels to blue with using
   // pixelWidth and pixelHeight
   for (int i = 0; i < pixelWidth * pixelHeight; i++) {
   pixels[i] = color(0, 0, 255);
   }
   // Fill one quarter of the pixels to yellow
   // because the pixel density is set to 2 in setup()
   // and 'width' and 'height' don't reflect the pixel 
   // dimensions of the sketch
   for (int i = 0; i < width * height; i++) {
   pixels[i] = color(255, 255, 0);
   }
   updatePixels();
   noLoop();
  }
  

• pixelHeight
• pixelDensity()
• displayDensity()