Lua:Class:Canvas

{} Class

class Canvas : CustomCanvas

The Canvas class represents a drawing surface.

A Canvas inherits from CustomCanvas and Object. It provides access to drawing tools such as Brush, Pen, and Font, and offers methods for drawing shapes, text, images, pixels, and copied regions.

Inheritance

Class	Inherits From	Description
Canvas	CustomCanvas	A drawing surface used to render shapes, text, images, and pixels.
CustomCanvas	Object	Base class for canvas objects.

Properties

Property	Type	Description
Brush	Brush	The brush object used for filling shapes and areas.
Pen	Pen	The pen object used for drawing lines and outlines.
Font	Font	The font object used for drawing text.
Width	Integer	The width of the canvas.
Height	Integer	The height of the canvas.
Handle	Integer	The device context handle of the canvas.

Methods

Method	Return Type	Description
getBrush()	Brush	Returns the brush object of this canvas.
getPen()	Pen	Returns the pen object of this canvas.
getFont()	Font	Returns the font object of this canvas.
getWidth()	Integer	Returns the width of the canvas.
getHeight()	Integer	Returns the height of the canvas.
getPenPosition()	Integer, Integer	Returns the current pen position.
setPenPosition(x, y)	void	Sets the current pen position.
clear()	void	Clears the canvas.
line(sourcex, sourcey, destinationx, destinationy)	void	Draws a line from the source coordinates to the destination coordinates.
lineTo(destinationx, destinationy)	void	Draws a line from the current pen position to the destination coordinates.
moveTo(destinationx, destinationy)	void	Moves the current pen position to the destination coordinates.
rect(x1, y1, x2, y2)	void	Draws a rectangle.
fillRect(x1, y1, x2, y2)	void	Draws a filled rectangle.
roundRect(x1, y1, x2, y2, rx, ry)	void	Draws a rectangle with rounded corners.
drawFocusRect(x1, y1, x2, y2)	void	Draws a focus rectangle shape.
textOut(x, y, text)	void	Draws text at the specified coordinates.
textRect(rect, x, y, text)	void	Writes text within the given rectangle. The text supports some ANSI escape characters.
getTextWidth(text)	Integer	Returns the width of the given text.
getTextHeight(text)	Integer	Returns the height of the given text.
getPixel(x, y)	Integer	Returns the color value of the pixel at the specified coordinates.
setPixel(x, y, color)	void	Sets the color value of the pixel at the specified coordinates.
floodFill(x, y, color, filltype)	void	Fills an area starting at the specified coordinates.
ellipse(x1, y1, x2, y2)	void	Draws an ellipse within the specified rectangle.
gradientFill(x1, y1, x2, y2, startcolor, stopcolor, direction)	void	Fills a rectangle with a gradient.
copyRect(dest_x1, dest_y1, dest_x2, dest_y2, sourceCanvas, source_x1, source_y1, source_x2, source_y2)	void	Draws an image from one canvas to another. This is useful for double buffering.
draw(x, y, graphic)	void	Draws the image of a specific Graphic class object.
stretchDraw(rect, graphic)	void	Draws the image of a specific Graphic class object and stretches it to fit inside the given rectangle.
getClipRect()	Table	Returns a table containing the fields Left, Top, Right, and Bottom, which define the invalidated region of the graphical object.

Flood Fill Types

Value	Description
fsSurface	Fills until the specified color is reached. It fills all connected pixels except this color.
fsBorder	Fills only connected pixels of the specified color.

Gradient Directions

Value	Direction	Description
0	Vertical	Creates a vertical gradient.
1	Horizontal	Creates a horizontal gradient.

Clip Rect Fields

Field	Type	Description
Left	Integer	The left edge of the invalidated region.
Top	Integer	The top edge of the invalidated region.
Right	Integer	The right edge of the invalidated region.
Bottom	Integer	The bottom edge of the invalidated region.

Examples

 1 local form = createForm()
 2 form.Caption = "Canvas Example"
 3 form.Width = 400
 4 form.Height = 300
 5 
 6 form.OnPaint = function(sender)
 7   local canvas = sender.Canvas
 8 
 9   canvas.Pen.Color = 0x0000FF
10   canvas.Brush.Color = 0xFFFFFF
11 
12   canvas.rect(20, 20, 180, 100)
13   canvas.textOut(30, 40, "Hello Canvas")
14 end
15 
16 form.show()

 1 local form = createForm()
 2 form.Caption = "Canvas Pixel Example"
 3 form.Width = 300
 4 form.Height = 200
 5 
 6 form.OnPaint = function(sender)
 7   local canvas = sender.Canvas
 8 
 9   canvas.setPixel(50, 50, 0x0000FF)
10 
11   local color = canvas.getPixel(50, 50)
12   canvas.textOut(20, 80, "Pixel color: " .. tostring(color))
13 end
14 
15 form.show()

 1 local form = createForm()
 2 form.Caption = "Canvas Clip Rect Example"
 3 form.Width = 400
 4 form.Height = 300
 5 
 6 form.OnPaint = function(sender)
 7   local canvas = sender.Canvas
 8   local clip = canvas.getClipRect()
 9 
10   canvas.textOut(20, 20, "Clip Left: " .. tostring(clip.Left))
11   canvas.textOut(20, 40, "Clip Top: " .. tostring(clip.Top))
12   canvas.textOut(20, 60, "Clip Right: " .. tostring(clip.Right))
13   canvas.textOut(20, 80, "Clip Bottom: " .. tostring(clip.Bottom))
14 end
15 
16 form.show()

 1 function drawRGBSpectrum(canvas, x, y, width, height)
 2   if canvas == nil then
 3     return
 4   end
 5 
 6   width = math.max(1, width or 256)
 7   height = math.max(1, height or 32)
 8 
 9   for px = 0, width - 1 do
10     local hue = px / math.max(1, width - 1)
11     local r, g, b
12 
13     if hue < 1 / 6 then
14       r = 255
15       g = math.floor(hue * 6 * 255)
16       b = 0
17     elseif hue < 2 / 6 then
18       r = math.floor((2 / 6 - hue) * 6 * 255)
19       g = 255
20       b = 0
21     elseif hue < 3 / 6 then
22       r = 0
23       g = 255
24       b = math.floor((hue - 2 / 6) * 6 * 255)
25     elseif hue < 4 / 6 then
26       r = 0
27       g = math.floor((4 / 6 - hue) * 6 * 255)
28       b = 255
29     elseif hue < 5 / 6 then
30       r = math.floor((hue - 4 / 6) * 6 * 255)
31       g = 0
32       b = 255
33     else
34       r = 255
35       g = 0
36       b = math.floor((1 - hue) * 6 * 255)
37     end
38 
39     local color = r + (g * 0x100) + (b * 0x10000)
40 
41     canvas.Pen.Color = color
42     canvas.line(x + px, y, x + px, y + height)
43   end
44 end
45 
46 local form = createForm()
47 form.Caption = "RGB Spectrum Canvas Example"
48 form.Width = 400
49 form.Height = 160
50 
51 form.OnPaint = function(sender)
52   local canvas = sender.Canvas
53 
54   drawRGBSpectrum(canvas, 20, 40, 340, 40)
55 
56   canvas.Font.Color = 0x000000
57   canvas.textOut(20, 90, "RGB Spectrum")
58 end
59 
60 form.show()

See Also

Main Pages

Lua
Script Engine