Function checkTint

test/unit/image/loading.js:275–312

(tintColor)

  });

  function checkTint(tintColor) {
    myp5.loadPixels();
    pImg.loadPixels();
    for (var i = 0; i < myp5.pixels.length; i += 4) {
      var x = (i / 4) % myp5.width;
      var y = Math.floor(i / 4 / myp5.width);
      for (var chan = 0; chan < tintColor.length; chan++) {
        var inAlpha = 1;
        var outAlpha = 1;
        if (chan < 3) {
          // The background of the canvas is black, so after applying the
          // image's own alpha + the tint alpha to its color channels, we
          // should arrive at the same color that we see on the canvas.
          inAlpha = tintColor[3] / 255;
          outAlpha = pImg.pixels[i + 3] / 255;

          // Applying the tint involves un-multiplying the alpha of the source
          // image, which causes a bit of loss of precision. I'm allowing a
          // loss of 10 / 255 in this test.
          assert.approximately(
            myp5.pixels[i + chan],
            pImg.pixels[i + chan] *
              (tintColor[chan] / 255) *
              outAlpha *
              inAlpha,
            10,
            'Tint output for the ' +
              chanNames[chan] +
              ' channel of pixel (' +
              x +
              ', ' +
              y +
              ') should be equivalent to multiplying the image value by tint fraction'
          );
        }
      }
    }
  }

  test('tint() with color', function() {
    assert.ok(pImg, 'image loaded');