Objective Caml module ``Graphics''

Module Graphics: machine-independent graphics primitives

exception Graphic_failure of string
Raised by the functions below when they encounter an error.


val open_graph: string -> unit
Show the graphics window or switch the screen to graphic mode. The graphics window is cleared and the current point is set to (0, 0). The string argument is used to pass optional information on the desired graphics mode, the graphics window size, and so on. Its interpretation is implementation-dependent. If the empty string is given, a sensible default is selected.
val close_graph: unit -> unit
Delete the graphics window or switch the screen back to text mode.
val clear_graph : unit -> unit
Erase the graphics window.
val size_x : unit -> int
val size_y : unit -> int
Return the size of the graphics window. Coordinates of the screen pixels range over 0 .. size_x()-1 and 0 .. size_y()-1. Drawings outside of this rectangle are clipped, without causing an error. The origin (0,0) is at the lower left corner.


type color = int
A color is specified by its R, G, B components. Each component is in the range 0..255. The three components are packed in an int: 0xRRGGBB, where RR are the two hexadecimal digits for the red component, GG for the green component, BB for the blue component.
val rgb: int -> int -> int -> color
rgb r g b returns the integer encoding the color with red component r, green component g, and blue component b. r, g and b are in the range 0..255.
val set_color : color -> unit
Set the current drawing color.
val black : color
val white : color
val red : color
val green : color
val blue : color
val yellow : color
val cyan : color
val magenta : color
Some predefined colors.
val background: color
val foreground: color
Default background and foreground colors (usually, either black foreground on a white background or white foreground on a black background). clear_graph fills the screen with the background color. The initial drawing color is foreground.

Point and line drawing

val plot : int -> int -> unit
Plot the given point with the current drawing color.
val point_color : int -> int -> color
Return the color of the given point.
val moveto : int -> int -> unit
Position the current point.
val current_point : unit -> int * int
Return the position of the current point.
val lineto : int -> int -> unit
Draw a line with endpoints the current point and the given point, and move the current point to the given point.
val draw_arc : int -> int -> int -> int -> int -> int -> unit
draw_arc x y rx ry a1 a2 draws an elliptical arc with center x,y, horizontal radius rx, vertical radius ry, from angle a1 to angle a2 (in degrees). The current point is unchanged.
val draw_ellipse : int -> int -> int -> int -> unit
draw_ellipse x y rx ry draws an ellipse with center x,y, horizontal radius rx and vertical radius ry. The current point is unchanged.
val draw_circle : int -> int -> int -> unit
draw_circle x y r draws a circle with center x,y and radius r. The current point is unchanged.
val set_line_width : int -> unit
Set the width of points and lines drawn with the functions above. Under X Windows, set_line_width 0 selects a width of 1 pixel and a faster, but less precise drawing algorithm than the one used when set_line_width 1 is specified.

Text drawing

val draw_char : char -> unit
val draw_string : string -> unit
Draw a character or a character string with lower left corner at current position. After drawing, the current position is set to the lower right corner of the text drawn.
val set_font : string -> unit
val set_text_size : int -> unit
Set the font and character size used for drawing text. The interpretation of the arguments to set_font and set_text_size is implementation-dependent.
val text_size : string -> int * int
Return the dimensions of the given text, if it were drawn with the current font and size.


val fill_rect : int -> int -> int -> int -> unit
fill_rect x y w h fills the rectangle with lower left corner at x,y, width w and height h, with the current color.
val fill_poly : (int * int) array -> unit
Fill the given polygon with the current color. The array contains the coordinates of the vertices of the polygon.
val fill_arc : int -> int -> int -> int -> int -> int -> unit
Fill an elliptical pie slice with the current color. The parameters are the same as for draw_arc.
val fill_ellipse : int -> int -> int -> int -> unit
Fill an ellipse with the current color. The parameters are the same as for draw_ellipse.
val fill_circle : int -> int -> int -> unit
Fill a circle with the current color. The parameters are the same as for draw_circle.


type image
The abstract type for images, in internal representation. Externally, images are represented as matrices of colors.
val transp : color
In matrices of colors, this color represent a ``transparent'' point: when drawing the corresponding image, all pixels on the screen corresponding to a transparent pixel in the image will not be modified, while other points will be set to the color of the corresponding point in the image. This allows superimposing an image over an existing background.
val make_image : color array array -> image
Convert the given color matrix to an image. Each sub-array represents one horizontal line. All sub-arrays must have the same length; otherwise, exception Graphic_failure is raised.
val dump_image : image -> color array array
Convert an image to a color matrix.
val draw_image : image -> int -> int -> unit
Draw the given image with lower left corner at the given point.
val get_image : int -> int -> int -> int -> image
Capture the contents of a rectangle on the screen as an image. The parameters are the same as for fill_rect.
val create_image : int -> int -> image
create_image w h returns a new image w pixels wide and h pixels tall, to be used in conjunction with blit_image. The initial image contents are random, except that no point is transparent.
val blit_image : image -> int -> int -> unit
blit_image img x y copies screen pixels into the image img, modifying img in-place. The pixels copied are those inside the rectangle with lower left corner at x,y, and width and height equal to those of the image. Pixels that were transparent in img are left unchanged.

Mouse and keyboard events

type status =
  { mouse_x : int;              (* X coordinate of the mouse *)
    mouse_y : int;              (* Y coordinate of the mouse *)
    button : bool;              (* true if a mouse button is pressed *)
    keypressed : bool;          (* true if a key has been pressed *)
    key : char }                (* the character for the key pressed *)
To report events.
type event =
    Button_down                 (* A mouse button is pressed *)
  | Button_up                   (* A mouse button is released *)
  | Key_pressed                 (* A key is pressed *)
  | Mouse_motion                (* The mouse is moved *)
  | Poll                        (* Don't wait; return immediately *)
To specify events to wait for.
val wait_next_event : event list -> status
Wait until one of the events specified in the given event list occurs, and return the status of the mouse and keyboard at that time. If Poll is given in the event list, return immediately with the current status. If the mouse cursor is outside of the graphics window, the mouse_x and mouse_y fields of the event are outside the range 0..size_x()-1, 0..size_y()-1. Keypresses are queued, and dequeued one by one when the Key_pressed event is specified.

Mouse and keyboard polling

val mouse_pos : unit -> int * int
Return the position of the mouse cursor, relative to the graphics window. If the mouse cursor is outside of the graphics window, mouse_pos() returns a point outside of the range 0..size_x()-1, 0..size_y()-1.
val button_down : unit -> bool
Return true if the mouse button is pressed, false otherwise.
val read_key : unit -> char
Wait for a key to be pressed, and return the corresponding character. Keypresses are queued.
val key_pressed : unit -> bool
Return true if a keypress is available; that is, if read_key would not block.


val sound : int -> int -> unit
sound freq dur plays a sound at frequency freq (in hertz) for a duration dur (in milliseconds).

This document was translated from LATEX by HEVEA.