Programming for Art: Images Dr. J. R. Parker Art/Digital Media Lab Lec 17 Fall 2010

Images Images are 2D arrays of pixels. Conceptually, this is clear, and so it should also be clear how to get a pixel value and set one. Images reside in files, GIF or JPEG or PNG etc etc, and so key issues with images in Processing involve reading the image and displaying it.

Images Images are added after other types in the language; they are a complex type, not a simple one, and is based on other types. An image variable is of type PImage (processing image)

Images PImage myImage; void setup () { size (300, 300); myImage = loadImage (“myimage.jpg”); } void draw() background (0); image (myImage, 0, 0);

Images The image file must be in the same directory as the source file, or you will need a path name in the quotes.

Images Load it at a different place each frame … void draw() { background (0); image (myImage, random(30), random(30)); }

Images Load a ball and bounce it PImage myImage; int x=0, y=100; int dx=1, dy=1; void setup () { size (300, 300); myImage = loadImage ("ball.gif"); } Images void draw() { background (0); x += dx; y += dy; image (myImage, x, y); if (x > width-32) dx = -1; else if (x <= 0) dx = 1; if (y > height-32) dy = -1; else if (y<=0) dy = 1; }

Multiple Images PImage myImage, backImage; int x=0, y=100; int dx=1, dy=1; void setup () { size (300, 300); backImage = loadImage ("back.jpg"); myImage = loadImage ("ball.gif"); } void draw() { background (0); x += dx; y += dy; image (backImage, 0, 0); image (myImage, x, y); if (x > width-32) dx = -1; else if (x <= 0) dx = 1; if (y > height-32) dy = -1; else if (y<=0) dy = 1; }

Multiple Images

The Display Window The display window is an Image!

Arrays of arrays This is a 2D array. How is it done? Memory, after all, is one dimensional. We do it by mapping 2D indices onto 1D ones. Column 0 1 2 3 4 5 6 7 Row 0 Row 1 Row 2 A 12

Arrays of arrays Advanced material: Array element A[i][j] is accessed as A + (i*Nrows)+j Column 0 1 2 3 4 5 6 7 Row 0 Row 1 Row 2 A 12

Advanced Material A + (i*Nrows)+j Row 0 Row 1 Row 2 0 1 2 3 4 5 6 7 A 0 1 2 3 4 5 6 7 A + (i*Nrows)+j Row 0 Row 1 Row 2 A A Col 0 Col 1 Col 2 12 A[1][2] = A+(1*Nrows)+2 = A+3+2 = A+5 12

What Use are 2D Arrays? An obvious item is that they can represent the screen. Each element could be a pixel