Shape adjustments

From Context Free Art

Contents 1 Shape Adjustments: Geometry and Color 1.1 Geometry Adjustments 1.2 Color Adjustments 1.2.1 Targeting a Color 1.2.1.1 Example: Targeting yellow 1.2.2 Some common hues

Shape Adjustments: Geometry and Color

There are two categories of shape adjustments: geometric and color. Anywhere that you see num there can either be a numeric constant or a constant expression.

Geometry Adjustments

The geometry of shapes is defined by a two dimensional affine transform which is represented internally as a matrix.

Adjustment	Meaning	Notes
x num	translation along the x-axis by num
y num	translation along the y-axis by num
z num	translation along the z-axis by num	The z-axis position determines which shape is on top when they overlap. The z-axis position is not stored in the affine transform matrix and does not affect the shape of objects.
size num or s num	scale in x and y by num
size num1 num2 or s num1 num2	scale in x by num1 and in y by num2
size num1 num2 num3 or s num1 num2 num3	scale in x by num1, in y by num2, and in z by num3	The z-axis scale is not stored in the affine transform matrix and does not affect the shape of objects.
rotate num or r num	rotate in the x/y plane num degrees
flip num or f num	reflect in x/y plane across a line through the origin at num degrees
skew num1 num2	shear transform in x/y plane num1 degrees from the y axis and num2 degrees from the x axis

Color Adjustments

The color of a shape is represented by two points in the HSBA color space (HSB color plus alpha, or opacity). One point is the color that the shape is actually drawn in and the other point is a target that the drawing color trends toward. The HSBA coordinates are [0,360) for hue, [0,1] for saturation, [0,1] for brightness, and [0,1] for alpha (opacity).

hue num

add num to the drawing hue value, modulo 360

saturation num

range [-1,1]. If num<0 then change the drawing saturation num% toward 0. If num>0 then change the drawing saturation num% toward 1.

brightness num

range [-1,1]. If num<0 then change the drawing brightness num% toward 0. If num>0 then change the drawing brightness num% toward 1.

alpha num

range [-1,1]. If num<0 then change the drawing alpha num% toward 0. If num>0 then change the drawing alpha num% toward 1.

|hue num

add num to the target hue value, modulo 360

|saturation num

range [-1,1]. If num<0 then change the target saturation num% toward 0. If num>0 then change the target saturation num% toward 1.

|brightness num

range [-1,1]. If num<0 then change the target brightness num% toward 0. If num>0 then change the target brightness num% toward 1.

|alpha num

range [-1,1]. If num<0 then change the target alpha num% toward 0. If num>0 then change the target alpha num% toward 1.

Abbreviations: 'hue' can be abbreviated as 'h', 'saturation' can be abbreviated as 'sat', 'brightness' can be abbreviated as 'b', and 'alpha' can be abbreviated as 'a'.

Targeting a Color

There are four more drawing color adjustments for changing the drawing color components with respect to the target color. This useful is you have a recursive shape rule that adjusts a color component and you don't want to overshoot a value. For example, the drawing hue is red and you want the drawing hue to trend toward yellow, but never go past yellow to green.

hue num|

range [-1,1]. If num<0 then change the drawing hue num% toward the target hue moving clockwise around the color wheel. If num>0 then change the drawing hue num% toward the target hue counter-clockwise around the color wheel.

saturation num|

range [-1,1]. If num<0 then change the drawing saturation num% toward 0 or the target saturation, whichever is closer. If num>0 then change the drawing saturation num% toward 1 or the target saturation, whichever is closer.

brightness num|

range [-1,1]. If num<0 then change the drawing brightness num% toward 0 or the target brightness, whichever is closer. If num>0 then change the drawing brightness num% toward 1 or the target brightness, whichever is closer.

alpha num|

range [-1,1]. If num<0 then change the drawing alpha num% toward 0 or the target alpha, whichever is closer. If num>0 then change the drawing alpha num% toward 1 or the target alpha, whichever is closer.

Example: Targeting yellow

For example, the following code applied consistently when drawing shapes, will change the initial hue 0 (red) quickly to yellow (hue 60) but not let it go past yellow towards green:

MyShape { h 60|h 0.99 } // yellow hues

More on targeting colors can be found in the tutorial Targeting a color.

Some common hues

Remember that the initial hue is always 0, i.e red. Some common hues follow:

Hue number	Primary	Secondary	Tertiary
0	Red
30			Orange ("Red-Yellow")
60		Yellow
90			Yellow-Green
120	Green
150			Aqua ("Green-Cyan")
180		Cyan
210			Turquoise ("Cyan-Blue")
240	Blue
270			Violet ("Blue-Magenta")
300		Magenta
330			Reddish Purple ("Magenta-Red")
360 (=0)	Red