2.2 Basic Pict Constructors

► |  | Slideshow: Figure and Presentation Tools

1 | Creating Slide Presentations
2 | Making Pictures
3 | Making Slides
4 | Typesetting Racket Code
5 | Animations
| Bibliography
| Index

▼ | 2 | Making Pictures

2.1 | Pict Datatype
2.2 | Basic Pict Constructors
2.3 | Pict Combiners
2.4 | Pict Drawing Adjusters
2.5 | Bounding Box Adjusters
2.6 | Pict Finders
2.7 | More Pict Constructors
2.8 | Miscellaneous
2.9 | Rendering
2.10 | Conversion to Picts

On this page:

dc
blank
text
hline
vline
frame
ellipse
circle
filled-ellipse
disk
rectangle
filled-rectangle
rounded-rectangle
filled-rounded-rectangle
bitmap
arrow
arrowhead
pip-line
pip-arrow-line
pip-arrows-line
pin-line
pin-arrow-line
pin-arrows-line
text-style/ c
bitmap-draft-mode

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#### 2.2`` Basic Pict Constructors

> procedure (dc draw w h) → pict?
> draw : ((is-a?/c dc<%>) real? real? . -> . any)
> w : real?
> h : real?
> (dc draw w h a d) → pict?
> draw : ((is-a?/c dc<%>) real? real? . -> . any)
> w : real?
> h : real?
> a : real?
> d : real?

Creates an arbitrary self-rendering pict. The arguments to the rendering procedure will be a drawing context and top-left location for drawing.

The w and h arguments determine the width and height of the resulting pict’s bounding box. In the three-argument case, the descent is 0 and the ascent is h for the bounding box; in the five-argument case, a and d are used as the bounding box’s ascent and descent.

When the rendering procedure is called, the current pen and brush will be solid and in the pict’s color (and linewidth), and the scale and offset of the drawing context will be set. The text mode will be transparent, but the font and text colors are not guaranteed to be anything in particular.

Example:
> > (dc (λ (dc dx dy)
> (define old-brush (send dc get-brush))
> (define old-pen (send dc get-pen))
> (send dc set-brush
> (new brush% [style 'fdiagonal-hatch]
> [color "darkslategray"]))
> (send dc set-pen
> (new pen% [width 3] [color "slategray"]))
> (define path (new dc-path%))
> (send path move-to 0 0)
> (send path line-to 50 0)
> (send path line-to 25 50)
> (send path close)
> (send dc draw-path path dx dy)
> (send dc set-brush old-brush)
> (send dc set-pen old-pen))
> 50 50)

> procedure (blank [size]) → pict?
> size : real? = 0
> (blank w h) → pict?
> w : real?
> h : real?
> (blank w a d) → pict?
> w : real?
> a : real?
> d : real?
> (blank w h a d) → pict?
> w : real?
> h : real?
> a : real?
> d : real?

Creates a pict that draws nothing. The one-argument case supplies a value used for both the width and height of the resulting pict’s bounding box. In the one- and two-argument case, the ascent and descent are 0 for the resulting pict’s bounding box; in the three-argument case, the height is computed by adding the given ascent and descent.

Example:
> > (blank 50)

> procedure (text content [style size angle]) → pict?
> content : string?
> style : text-style/c = null
> size : (integer-in 1 1024) = 12
> angle : real? = 0

Creates a pict that draws text. For creating text picts within a slide presentation, see t. The size of the resulting pict may depend on the value of dc-for-text-size.

The style argument must be one of the following:

- null — the default, same as 'default

- a font% object

- a font family symbol, such a 'roman (see font%)

- a font face string, such as "Helvetica" (see font%)

- (cons str sym) combining a face string and a font family (in case the face is unavailable; see font%)

- (cons 'bold style) for a valid style

- (cons 'italic style)

- (cons 'subscript style)

- (cons 'superscript style)

- (cons 'caps style)

- (cons 'combine style) — allows kerning and ligatures (the default, unless the 'modern family is specified)

- (cons 'no-combine style) — renders characters individually

- (cons 'aligned style) — enables hinting, which rounds metrics to integers

- (cons 'unaligned style) — disables hinting (which is the default), so that metrics are scalable

- (cons color style) — where color is a color% object, colorizes the text

If both 'combine and 'no-combine are specified, the first one in style takes precedence. Similarly, if both 'aligned and 'unaligned are specified, the first one in style takes precedence. If 'caps is specified, the angle must be zero.

The given size is in pixels, but it is ignored if a font% object is provided in the text-style.

The angle is in radians, and positive values rotate counter-clockwise. For a non-zero angle, the resulting pict’s bounding box covers the rotated text, and the descent is zero and the ascent is the height.

Examples:
> > (text "tom collins")
> > (text "g & t" (cons 'bold 'roman))
> > (text "martini" null 13 (/ pi 2))

> procedure (hline w h [#:segment seg-length]) → pict?
> w : real?
> h : real?
> seg-length : (or/c #f real?) = #f
> (vline w h [#:segment seg-length]) → pict?
> w : real?
> h : real?
> seg-length : (or/c #f real?) = #f

Straight lines, centered within their bounding boxes.

Examples:
> > (hline 40 5)
> > (vline 5 40 #:segment 5)

> > procedure
> > (frame |  | pict |  |  |  |
> > | [ | #:segment seg-length |  |  |  |
> > |  | #:color color |  |  |  |
> > |  | #:line-width width]) |  | → |  | pict?
> pict : pict?
> seg-length : (or/c #f real?) = #f
> color : (or/c #f string? (is-a?/c color<%>)) = #f
> width : (or/c #f real?) = #f

Frames a given pict. If the color or line width are provided, the override settings supplied by the context.

Examples:
> > (frame (circle 30))
> > (frame (circle 30) #:segment 5)
> > (frame (circle 30) #:color "chartreuse" #:line-width 3)

> procedure (ellipse w h) → pict?
> w : real?
> h : real?
> (circle diameter) → pict?
> diameter : real?
> (filled-ellipse |  | w |  |  |  |
> |  | h |  |  |  |
> | [ | #:draw-border? draw-border?]) |  | → |  | pict?
> w : real?
> h : real?
> draw-border? : any/c = #t
> (disk diameter [#:draw-border? draw-border?]) → pict?
> diameter : real?
> draw-border? : any/c = #t

Unfilled and filled ellipses.

If draw-border? is #f, then the pen is set to be transparent before drawing the ellipse.

Examples:
> > (ellipse 40 30)
> > (circle 30)
> > (filled-ellipse 30 40)
> > (disk 30)

> procedure (rectangle w h) → pict?
> w : real?
> h : real?
> (filled-rectangle |  | w |  |  |  |
> |  | h |  |  |  |
> | [ | #:draw-border? draw-border?]) |  | → |  | pict?
> w : real?
> h : real?
> draw-border? : any/c = #t

Unfilled and filled rectangles.

If draw-border? is #f, then the pen is set to be transparent before drawing the rectangle.

Examples:
> > (rectangle 50 50)
> > (filled-rectangle 50 80)

> > procedure
> > (rounded-rectangle |  | w |  |  |  |
> > |  | h |  |  |  |
> > | [ | corner-radius |  |  |  |
> > |  | #:angle angle]) |  | → |  | pict?
> w : real?
> h : real?
> corner-radius : real? = -0.25
> angle : real? = 0
> (filled-rounded-rectangle |  | w |  |  |  |
> |  | h |  |  |  |
> | [ | corner-radius |  |  |  |
> |  | #:angle angle |  |  |  |
> |  | #:draw-border? draw-border?]) |  | → |  | pict?
> w : real?
> h : real?
> corner-radius : real? = -0.25
> angle : real? = 0
> draw-border? : any/c = #t

Unfilled and filled rectangles with rounded corners. The corner-radius is used to determine how much rounding occurs in the corners. If it is a positive number, then it determines the radius of a circle touching the edges in each corner, and the rounding of the rectangle follow the edge of those circles. If it is a negative number, then the radius of the circles in the corners is the absolute value of the corner-radius times the smaller of width and height.

The angle determines how much the rectangle is rotated, in radians.

If draw-border? is #f, then the pen is set to be transparent before drawing the rectangle.

Examples:
> > (rounded-rectangle 40 40 -0.3 #:angle (/ pi 4))
> > (filled-rounded-rectangle 50 40)

> procedure (bitmap img) → pict
> | img |  | : |  |
> (or/c path-string?
> (is-a?/c bitmap%)
> (is-a?/c image-snip%))

A pict that display a bitmap. When a path is provided, the image is loaded with the 'unknown/mask flag, which means that a mask bitmap is generated if the file contains a mask.

If the bitmap cannot be loaded, if the given bitmap% object is not valid, or if the bitmap-draft-mode parameter is set to #t, the result pict draws the word “bitmap failed”.

> procedure (arrow size radians) → pict?
> size : real?
> radians : real?
> (arrowhead size radians) → pict?
> size : real?
> radians : real?

Creates an arrow or arrowhead in the specific direction within a size by size pict. Points on the arrow may extend slightly beyond the bounding box.

Examples:
> > (arrow 30 0)
> > (arrow 30 (/ pi 2))
> > (arrowhead 30 0)

> procedure (pip-line dx dy size) → pict?
> dx : real?
> dy : real?
> size : real?
> (pip-arrow-line dx dy size) → pict?
> dx : real?
> dy : real?
> size : real?
> (pip-arrows-line dx dy size) → pict?
> dx : real?
> dy : real?
> size : real?

Creates a line (with some number of arrowheads) as a zero-sized pict suitable for use with pin-over. The 0-sized picture contains the starting point.

The size is used for the arrowhead size. Even though pip-line creates no arrowheads, it accepts the size argument for consistency with the other functions.

> > procedure
> > (pin-line |  | pict |  |  |  |
> > |  | src |  |  |  |
> > |  | find-src |  |  |  |
> > |  | dest |  |  |  |
> > |  | find-dest |  |  |  |
> > | [ | #:start-angle start-angle |  |  |  |
> > |  | #:end-angle end-angle |  |  |  |
> > |  | #:start-pull start-pull |  |  |  |
> > |  | #:end-pull end-pull |  |  |  |
> > |  | #:line-width line-width |  |  |  |
> > |  | #:color color] |  |  |  |
> > |  | #:alpha alpha |  |  |  |
> > | [ | #:style style |  |  |  |
> > |  | #:under? under?]) |  | → |  | pict?
> pict : pict?
> src : pict-path?
> find-src : (pict? pict-path? . -> . (values real? real?))
> dest : pict-path?
> find-dest : (pict? pict-path? . -> . (values real? real?))
> start-angle : (or/c real? #f) = #f
> end-angle : (or/c real? #f) = #f
> start-pull : real? = 1/4
> end-pull : real? = 1/4
> line-width : (or/c #f real?) = #f
> color : (or/c #f string? (is-a?/c color%)) = #f
> alpha : (real-in 0.0 1.0)
> | style |  | : |  |
> (one-of/c 'transparent 'solid 'xor 'hilite
> 'dot 'long-dash 'short-dash 'dot-dash
> 'xor-dot 'xor-long-dash 'xor-short-dash
> 'xor-dot-dash)
> |  |  | = |  | 'solid
> under? : any/c = #f
> (pin-arrow-line |  | arrow-size |  |  |  |
> |  | pict |  |  |  |
> |  | src |  |  |  |
> |  | find-src |  |  |  |
> |  | dest |  |  |  |
> |  | find-dest |  |  |  |
> | [ | #:start-angle start-angle |  |  |  |
> |  | #:end-angle end-angle |  |  |  |
> |  | #:start-pull start-pull |  |  |  |
> |  | #:end-pull end-pull |  |  |  |
> |  | #:line-width line-width |  |  |  |
> |  | #:color color] |  |  |  |
> |  | #:alpha alpha |  |  |  |
> | [ | #:style style |  |  |  |
> |  | #:under? under? |  |  |  |
> |  | #:solid? solid?] |  |  |  |
> |  | #:hide-arrowhead? any/c) |  | → |  | pict?
> arrow-size : real?
> pict : pict?
> src : pict-path?
> find-src : (pict? pict-path? . -> . (values real? real?))
> dest : pict-path?
> find-dest : (pict? pict-path? . -> . (values real? real?))
> start-angle : (or/c real? #f) = #f
> end-angle : (or/c real? #f) = #f
> start-pull : real? = 1/4
> end-pull : real? = 1/4
> line-width : (or/c #f real?) = #f
> color : (or/c #f string? (is-a?/c color%)) = #f
> alpha : (real-in 0.0 1.0)
> | style |  | : |  |
> (one-of/c 'transparent 'solid 'xor 'hilite
> 'dot 'long-dash 'short-dash 'dot-dash
> 'xor-dot 'xor-long-dash 'xor-short-dash
> 'xor-dot-dash)
> |  |  | = |  | 'solid
> under? : any/c = #f
> solid? : any/c = #t
> any/c : #f
> (pin-arrows-line |  | arrow-size |  |  |  |
> |  | pict |  |  |  |
> |  | src |  |  |  |
> |  | find-src |  |  |  |
> |  | dest |  |  |  |
> |  | find-dest |  |  |  |
> | [ | #:start-angle start-angle |  |  |  |
> |  | #:end-angle end-angle |  |  |  |
> |  | #:start-pull start-pull |  |  |  |
> |  | #:end-pull end-pull |  |  |  |
> |  | #:line-width line-width |  |  |  |
> |  | #:color color] |  |  |  |
> |  | #:alpha alpha |  |  |  |
> |  | #:style style |  |  |  |
> | [ | #:under? under? |  |  |  |
> |  | #:solid? solid?] |  |  |  |
> |  | #:hide-arrowhead? any/c) |  | → |  | pict?
> arrow-size : real?
> pict : pict?
> src : pict-path?
> find-src : (pict? pict-path? . -> . (values real? real?))
> dest : pict-path?
> find-dest : (pict? pict-path? . -> . (values real? real?))
> start-angle : (or/c real? #f) = #f
> end-angle : (or/c real? #f) = #f
> start-pull : real? = 1/4
> end-pull : real? = 1/4
> line-width : (or/c #f real?) = #f
> color : (or/c #f string? (is-a?/c color%)) = #f
> alpha : (real-in 0.0 1.0)
> | style |  | : |  |
> (one-of/c 'transparent 'solid 'xor 'hilite
> 'dot 'long-dash 'short-dash 'dot-dash
> 'xor-dot 'xor-long-dash 'xor-short-dash
> 'xor-dot-dash)
> under? : any/c = #f
> solid? : any/c = #t
> any/c : #f

Adds a line or line-with-arrows onto pict, using one of the pict-finding functions (e.g., lt-find) to extract the source and destination of the line.

If under? is true, then the line and arrows are added under the existing pict drawing, instead of on top. If solid? is false, then the arrowheads are hollow instead of filled.

The start-angle, end-angle, start-pull, and end-pull arguments control the curve of the line (and the defaults produce a straight line):

- The start-angle and end-angle arguments specify the direction of curve at its start and end positions; if either is #f, it defaults to the angle of a straight line from the start position to end position.

- The start-pull and end-pull arguments specify a kind of momentum for the starting and ending angles; larger values preserve the angle longer.

The line-width, color, alpha, and style arguments apply to the added line.

When the hide-arrowhead? argument is a true value, then space for an arrowhead is kept around the line, but the arrowhead itself is not drawn.

Examples:
> (define pict-a (rectangle 40 40))
> (define pict-b (circle 40))
> (define combined (hc-append 200 pict-a pict-b))
> > (pin-line combined
> pict-a cc-find
> pict-b cc-find)
> > (pin-arrow-line 30 combined
> pict-a rc-find
> pict-b lc-find
> #:line-width 3
> #:style 'long-dash
> #:color "medium goldenrod")
> > (pin-arrows-line 30 combined
> pict-a rc-find
> pict-b lc-find
> #:start-angle (/ pi 11)
> #:end-angle (- (/ pi 11))
> #:solid? #f)

> value text-style/c : contract?

A contract that matches the second argument of text.

> parameter (bitmap-draft-mode) → boolean?
> (bitmap-draft-mode on?) → void?
> on? : any/c

A parameter that determines whether bitmap loads/uses a bitmap.
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