Programming Course for Beginners - ZedLX

Drawing on Images

The getter function .atleast from type int returns a value greater than the argument.

A getter like .atleast cannot modify the variable it is acting upon ('val').

The only way to change the variable is to employ the assignment statement.

A new image is initially fully transparent.

The getter function .fill from type image returns an image filled with the given color.

A getter like .fill cannot modify the variable it is acting upon ('canvas').

The only way to change the variable is to employ the assignment statement.

Auto-assignment makes it easier to draw on an image.

The getter function .text from type image returns a new image with text drawn on it. The signature of procedure .text is:

• image image.text(
• • point2D position, (top-left corner)
  • fontTag font,
  • num fontSize,
  • colorA color,
  • string text
  • )

The procedure boxFillp fills a rectangular area of the screen. The signature of procedure boxFillp is:

• void boxFillp(
• • point2D position, (top-left corner)
  • vector2D size,
  • colorA color
  • )

The word void specifies that this procedure does not return a value.

The corresponding member function named .boxFill is available from type image. This member function returns the resulting image. Because of this it has a slightly different signature (it returns a value of type image).

The procedure boxEdgep fills an edge of a rectangular area.

The signature of procedure boxEdgep is:

• void boxEdgep(
• • point2D position, (top-left corner)
  • vector2D size,
  • num edgeWidth,
  • colorA color
  • )

The corresponding member function named .boxEdge is available from type image. This member function returns the resulting image. Because of this it has a slightly different signature (it returns a value of type image).

The getter function .crop from type image returns the specified part of the image.

The signature of this getter function is:

• image image.crop(
• • int x, (top)
  • int y, (left)
  • int sizeX,
  • int sizeY
  • )

The first word of the signatures specifies the type of the return value. In other words, this function produces a new value of type image. All getter functions must return a value.

The name image before the dot specifies what type does this function belong to.

The getter function .cropResize from type image returns a specified part of the image an resizes it to form a new image.

The signature of this getter function is:

• image image.cropResize(
• • point2D position, (top-left corner)
  • vector2D size,
  • int resultSizeX,
  • int resultSizeY
  • )

The getter function .putImage from type image puts one image onto another.

The signature of this getter function is:

• image image.putImage(
• • image img,
  • point2D p
  • )

The getter function .tile from type image creates a new image made of tiled copies of another image.

The signature of this getter function is:

• image image.tile(
• • int resultSizeX,
  • int resultSizeY,
  • point2D position
  • )

This program creates a small image with a red-blue gradient. It displays the gradient, and also displays a larger version of the gradient.

It then proceeds to create a large image created by tiling the gradient.

This development of the previous program creates a sprite from the tiled gradient.

It then proceeds animate the the sprite in a circular motion.

This development of the previous program counter-spins the sprite very fast. It also makes the sprite grow in size and makes it approach the center of the screen.