Predefined Functions – rgba
|Function name:||rgba – Create color from real arguments|
|Input data type||Output data type|
|real, real, real, real||color|
rgba(<red>,<green>,<blue>,<alpha>) returns a color which is initialized according to the four parameters passed to the function. The parameters
<alpha> should be in the range from 0 to 1. The alpha value of the color sets the transparency of the color: 0 means: color is transparent, 1 means, color is opaque.
rgba(0,0,0,1) returns an opaque black color,
rgb(1,1,1,1) returns an opaque white. On initializing the color no bounds checking is done, so
rgb(5,0,0,1) creates a color whose red-part is beyond the valid range. On output the value will be truncated to a correct interval (i.e.
rgb(1,0,0,1). But some other functions like the merging functions do not truncate a color in any way: They then will use that value.
So it’s legal to create colors whose parts are not in the valid range from 0 to 1, but you should know what you do…