▼Graphics: Legacy Library
►4 Draw, Clear, and Flip Operations
On this page:
4.1 Viewports
draw-viewport
clear-viewport
flip-viewport
copy-viewport
4.2 Pixels
draw-pixel
clear-pixel
flip-pixel
4.3 Lines
draw-line
clear-line
flip-line
4.4 Rectangles
draw-rectangle
clear-rectangle
flip-rectangle
draw-solid-rectangle
clear-solid-rectangle
flip-solid-rectangle
4.5 Ellipses
draw-ellipse
clear-ellipse
flip-ellipse
draw-solid-ellipse
clear-solid-ellipse
flip-solid-ellipse
4.6 Polygons
draw-polygon
clear-polygon
flip-polygon
draw-solid-polygon
clear-solid-polygon
flip-solid-polygon
4.7 Strings
draw-string
clear-string
flip-string
4.8 Pixmaps
draw-pixmap-posn
draw-pixmap
save-pixmap
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4 Draw, Clear, and Flip Operations

The following are the basic graphics operations for drawing to a viewport. Each function takes a viewport as its argument and returns a function operating within that viewport. Further arguments, if any, are curried. For example, (draw-line viewport) returns a function, that can then be applied to the proper arguments to draw a line in the viewport corresponding to viewport descriptor viewport.

In general, draw- functions make pixels black or colored, clear- functions make them white, and flip- commands invert pixels (which makes black white, white black, and is otherwise ill-defined).

4.1 Viewports

((draw-viewport viewport) [color]) → void?
  viewport : viewport?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Colors the entire contents of viewport with color.

((clear-viewport viewport)) → void?
  viewport : viewport?
Whitens the entire contents of viewport.

((flip-viewport viewport)) → void?
  viewport : viewport?
Inverts the entire contents of viewport.

(copy-viewport source dest) → void?
  source : viewport?
  dest : viewport?
Copies the content of source into dest.

4.2 Pixels

((draw-pixel viewport) p [color]) → void?
  viewport : viewport?
  p : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Colors the pixel in viewport at p.

((clear-pixel viewport) p) → void?
  viewport : viewport?
  p : posn?
Whitens the pixel in viewport at p.

((flip-pixel viewport) p) → void?
  viewport : viewport?
  p : posn?
Inverts the pixel in viewport at p.

4.3 Lines

((draw-line viewport) p1 p2 [color]) → void?
  viewport : viewport?
  p1 : posn?
  p2 : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a line in viewport connecting positions p1 and p2.

((clear-line viewport) p1 p2) → void?
  viewport : viewport?
  p1 : posn?
  p2 : posn?
Whitens a line in viewport connecting positions p1 and p2.

((flip-line viewport) p1 p2) → void?
  viewport : viewport?
  p1 : posn?
  p2 : posn?
Inverts a line in viewport connecting positions p1 and p2.

4.4 Rectangles

((draw-rectangle viewport)    
  p    
  width    
  height    
  [color]) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a rectangle border in the viewport with the top-left of the rectangle at the position p and with sides width across and height tall.

((clear-rectangle viewport) p width height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Whitens a rectangle border in the viewport, analogous to draw-rectangle.

((flip-rectangle viewport) p width height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Inverts a rectangle border in the viewport, analogous to draw-rectangle.

((draw-solid-rectangle viewport)    
  p    
  width    
  height    
  [color]) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a solid rectangle in the viewport with the top-left of the rectangle at the position p and with sides width across and height tall.

((clear-solid-rectangle viewport)    
  p    
  width    
  height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Whitens a rectangle border in the viewport, analogous to draw-solid-rectangle.

((flip-solid-rectangle viewport)    
  p    
  width    
  height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Inverts a rectangle border in the viewport, analogous to draw-solid-rectangle.

4.5 Ellipses

((draw-ellipse viewport) p width height [color]) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a ellipse border in the viewport. The ellipse is inscribed with a rectangle whose top-left is at position p and with sides width across and height tall.

((clear-ellipse viewport) p width height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Whitens a ellipse border in the viewport, analogous to draw-ellipse.

((flip-ellipse viewport) p width height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Inverts a ellipse border in the viewport, analogous to draw-ellipse.

((draw-solid-ellipse viewport)    
  p    
  width    
  height    
  [color]) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a solid ellipse in the viewport. The ellipse is inscribed with a rectangle whose top-left is at position p and with sides width across and height tall.

((clear-solid-ellipse viewport)    
  p    
  width    
  height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Whitens a ellipse border in the viewport, analogous to draw-solid-ellipse.

((flip-solid-ellipse viewport)    
  p    
  width    
  height) → void?
  viewport : viewport?
  p : posn?
  width : (and/c real? (not/c negative?))
  height : (and/c real? (not/c negative?))
Inverts a ellipse border in the viewport, analogous to draw-solid-ellipse.

4.6 Polygons

((draw-polygon viewport) points offset [color]) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a polygon border in viewport using points for the polygon vertices and offset as an offset added to all points.

((clear-polygon viewport) points offset) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
Whitens a polygon border in viewport, analogous to draw-polygon.

((flip-polygon viewport) points offset) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
Inverts a polygon border in viewport, analogous to draw-polygon.

((draw-solid-polygon viewport)    
  points    
  offset    
  [color]) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a solid polygon in viewport using points for the polygon vertices and offset as an offset added to all points.

((clear-solid-polygon viewport)    
  points    
  offset) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
Whitens a polygon border in viewport, analogous to draw-solid-polygon.

((flip-solid-polygon viewport)    
  points    
  offset) → void?
  viewport : viewport?
  points : (listof posn?)
  offset : posn?
Inverts a polygon border in viewport, analogous to draw-solid-polygon.

4.7 Strings

((draw-string viewport) p str [color]) → void?
  viewport : viewport?
  p : posn?
  str : string?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a string at a specified location in the viewport. The lower left of the string begins at p.

((clear-string viewport) p str) → void?
  viewport : viewport?
  p : posn?
  str : string?
Whitens a string at a specified location in the viewport. The lower left of the string begins at p.

((flip-string viewport) p str) → void?
  viewport : viewport?
  p : posn?
  str : string?
Inverts a string at a specified location in the viewport. The lower left of the string begins at p.

4.8 Pixmaps

(((draw-pixmap-posn file    
  [type]))    
  viewport)    
  p    
  [color]) → void?
  file : path-string?
  type : 
(one-of/c 'unknown 'unknown/mask
          'gif 'gif/mask 'jpeg 'png 'png/mask
          'xbm 'xpm 'bmp)
   = 'unknown/mask
  viewport : viewport?
  p : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Draws a pixmap into viewport with its upper left corner at position p. If type is 'unknown or 'unknown/mask, then the content of the file is examined to determine the type. The 'gif/mask, 'png/mask, and 'unknown/mask types draw the bitmap with a transparent background if filename refers to a GIF/PNG file with a transparent background.

The argument color is only used when the loaded pixmap is monochrome. In that case, the color is used instead of black in the drawn image.

((draw-pixmap viewport) file p [color]) → void?
  viewport : viewport?
  file : path-string?
  p : posn?
  color : 
(or/c (integer-in 0 299)
      string?
      rgb?)
 = "black"
Equivalent to (((draw-pixmap-posn file) viewport) p color).

((save-pixmap viewport) file [type]) → void?
  viewport : viewport?
  file : path-string?
  type : (one-of/c 'gif 'jpeg 'png 'xbm 'xpm 'bmp) = 'xpm
Saves the current content of viewport to file. The type argument determines the kind of file that is written.

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