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Rectangular grids - choosing colors from an image

This activity has the following desired goals:

  • Learning to color a rectangular grid using colors from an image (A, M).
  • Making interesting grid based designs (M, T).

Step 1

Type in the following code and run it:

size(600, 600)
cleari()
originBottomLeft()
val offWhite = cm.hex(0xF2F5F1)
setBackground(offWhite)

val tileCount = 100
val tileSize = cwidth / tileCount

val img = image("some-image.png")
def colorFromImage(x: Double, y: Double) = {
    val nx = mathx.map(x, 0, cwidth, 0, img.getWidth).toInt
    val ny = mathx.map(y, 0, cheight, 0, img.getHeight).toInt
    getImagePixel(img, nx, ny)
}

def cellColor(x: Double, y: Double) = colorFromImage(x, y)

def shape = Picture.rectangle(tileSize, tileSize)

def block(posX: Double, posY: Double) {
    val pic = shape
    pic.setPosition(posX, posY)
    pic.setPenColor(cm.tomato)
    pic.rotate(random(-5, 5))
    pic.scale(randomDouble(0.95, 1.1))
    pic.setFillColor(cellColor(posX, posY))
    pic.setPenThickness(0)
//    pic.setPenColor(offWhite)
    draw(pic)
}

repeatFor(rangeTill(0, cheight, tileSize)) { posY =>
    repeatFor(rangeTill(0, cwidth, tileSize)) { posX =>
        block(posX, posY)
    }
}

Q1a. Read through the code above and try to understand what it does. What does the above code do? How does it do it?

Explanation

The key idea for getting the color for a grid position from an image is shown in the following code:

val img = image("some-image.png")
def imgColor(x: Double, y: Double) = {
    val nx = mathx.map(x, 0, cwidth, 0, img.getWidth).toInt
    val ny = mathx.map(y, 0, cheight, 0, img.getHeight).toInt
    getImagePixel(img, nx, ny)
}

For any grid position, the color from the corresponding position in the image can be obtained via the imgColor function defined above. This function makes use of mathx.map(value, low1, high1, low2, high2) to do its work. mathx.map maps the given value from the range (low1, high1) to the range (low2, high2).


Exercise

Write a program to make a design using the above ideas.


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