Processing: Creative Coding and Computational Art

The mask works like an alpha channel. A value of 0 (black) will conceal the image pixel,
while a value of 255 (white) will fully reveal the image pixel. Values between 0 and 255 will
display the masked pixels in the image with varying degrees of translucency. In the next
sketch, I used one image to mask out the sky area of another image, allowing the display
window background color to show through (where the 0 values of the mask pixels are). I
made the sky-shaped mask image from the original image, which I was able to select and
convert using Photoshop. In the two example images, the first image uses a 100 percent
black sky mask, while the second uses a linear gradient from black (top of the sky) to white
(bottom of the sky). The two images I used were both 600 ✕ 480 pixels (see Figures 10-33
and 10-34):
// Mask the Sky
size(600, 480);
background(185, 185, 250);
PImage img = loadImage("harbor2.jpg");
PImage mask = loadImage("harbor2_mask.jpg");
img.mask(mask);
image(img, 0, 0, 600, 480);
Figure 10-33. Mask the Sky sketch
COLOR AND IMAGING
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