cairo2 0.5 · OCaml Package

Paint (and also mask and brush) with which cairo draws and associated function.

type 'a t constraint 'a = [< `Solid | `Surface | `Gradient | `Linear | `Radial ]

This is the paint with which cairo draws. The primary use of patterns is as the source for all cairo drawing operations, although they can also be used as masks, that is, as the brush too.

A cairo pattern is created by using one of the many functions, of the form Cairo.Pattern.create_type or implicitly through Cairo.set_source_* functions.

type any = [ `Solid | `Surface | `Gradient | `Linear | `Radial ] t

Cairo.Group.pop and Cairo.get_source retrieve patterns whose properties we do not know. In this case, we can only assume the pattern has potentially all properties and the functions below may raise an exception if it turns out that the needed property is not present.

val add_color_stop_rgb : 
  [> `Gradient ] t ->
  ?ofs:float ->
  float ->
  float ->
  float ->
  unit

Adds an opaque color stop to a gradient pattern. The offset ofs specifies the location along the gradient's control vector (default: 0.0). For example, a linear gradient's control vector is from (x0,y0) to (x1,y1) while a radial gradient's control vector is from any point on the start circle to the corresponding point on the end circle.

The color is specified in the same way as in Cairo.set_source_rgb.

If two (or more) stops are specified with identical offset values, they will be sorted according to the order in which the stops are added (stops added earlier will compare less than stops added later). This can be useful for reliably making sharp color transitions instead of the typical blend.

val add_color_stop_rgba : 
  [> `Gradient ] t ->
  ?ofs:float ->
  float ->
  float ->
  float ->
  float ->
  unit

Adds a translucent color stop to a gradient pattern. The offset specifies the location along the gradient's control vector. For example, a linear gradient's control vector is from (x0,y0) to (x1,y1) while a radial gradient's control vector is from any point on the start circle to the corresponding point on the end circle.

The color is specified in the same way as in Cairo.set_source_rgba.

val get_color_stop_count : [> `Gradient ] t -> int

Return the number of color stops specified in the given gradient pattern.

val get_color_stop_rgba : 
  [> `Gradient ] t ->
  idx:int ->
  float * float * float * float * float

Gets the color and offset information at the given index for a gradient pattern. Values of index are 0 to 1 less than the number returned by Cairo.Pattern.get_color_stop_count.

returns
(offset, red, green, blue, alpha)

val create_rgb : r:float -> g:float -> b:float -> [ `Solid ] t

Creates a new Cairo.Pattern.t corresponding to an opaque color. The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

val create_rgba : r:float -> g:float -> b:float -> a:float -> [ `Solid ] t

Creates a new Cairo.Pattern.t corresponding to a translucent color. The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

val get_rgba : [> `Solid ] t -> float * float * float * float

Return the solid color for a solid color pattern.

returns
(red, green, blue, alpha)

val create_for_surface : Surface.t -> [ `Surface ] t

Create a new Cairo.Pattern.t for the given surface.

val get_surface : [ `Surface ] t -> Surface.t

Gets the surface of a surface pattern.

val create_linear : 
  x0:float ->
  y0:float ->
  x1:float ->
  y1:float ->
  [ `Linear | `Gradient ] t

Create a new linear gradient Cairo.Pattern.t along the line defined by (x0, y0) and (x1, y1). Before using the gradient pattern, a number of color stops should be defined using Cairo.Pattern.add_color_stop_rgb or Cairo.Pattern.add_color_stop_rgba.

Note: The coordinates here are in pattern space. For a new pattern, pattern space is identical to user space, but the relationship between the spaces can be changed with Cairo.Pattern.set_matrix.

val get_linear_points : 
  [> `Linear | `Gradient ] t ->
  float * float * float * float

Gets the gradient endpoints for a linear gradient.

returns
(x0, y0, x1, y1).

val create_radial : 
  x0:float ->
  y0:float ->
  r0:float ->
  x1:float ->
  y1:float ->
  r1:float ->
  [ `Radial | `Gradient ] t

Creates a new radial gradient Cairo.Pattern.t between the two circles defined by (cx0, cy0, radius0) and (cx1, cy1, radius1). Before using the gradient pattern, a number of color stops should be defined using Cairo.Pattern.add_color_stop_rgb or Cairo.Pattern.add_color_stop_rgba.

Note: The coordinates here are in pattern space. For a new pattern, pattern space is identical to user space, but the relationship between the spaces can be changed with Cairo.Pattern.set_matrix.

val get_radial_circles : 
  [> `Radial | `Gradient ] t ->
  float * float * float * float * float * float

Gets the gradient endpoint circles for a radial gradient, each specified as a center coordinate and a radius.

returns
(x0, y0, r0, x1, y1, r1).

type extend =

| NONE
(*
pixels outside of the source pattern are fully transparent.
*)
| REPEAT
(*
the pattern is tiled by repeating.
*)
| REFLECT
(*
the pattern is tiled by reflecting at the edges.
*)
| PAD
(*
pixels outside of the pattern copy the closest pixel from the source.
*)

This is used to describe how pattern color/alpha will be determined for areas "outside" the pattern's natural area (for example, outside the surface bounds or outside the gradient geometry).

val set_extend : 'a t -> extend -> unit

Sets the mode to be used for drawing outside the area of a pattern. See Cairo.Pattern.extend for details on the semantics of each extend strategy.

The default extend mode is NONE for surface patterns and PAD for gradient patterns.

val get_extend : 'a t -> extend

Gets the current extend mode for a pattern. See Cairo.Pattern.extend for details on the semantics of each extend strategy.

type filter =

| FAST
(*
A high-performance filter, with quality similar to NEAREST
*)
| GOOD
(*
A reasonable-performance filter, with quality similar to BILINEAR
*)
| BEST
(*
The highest-quality available, performance may not be suitable for interactive use.
*)
| NEAREST
(*
Nearest-neighbor filtering
*)
| BILINEAR
(*
Linear interpolation in two dimensions
*)

This is used to indicate what filtering should be applied when reading pixel values from patterns. See Cairo.Pattern.set_filter for indicating the desired filter to be used with a particular pattern.

val set_filter : 'a t -> filter -> unit

Sets the filter to be used for resizing when using this pattern. See Cairo.Pattern.filter for details on each filter.

Note that you might want to control filtering even when you do not have an explicit Cairo.Pattern.t value (for example when using Cairo.set_source_surface). In these cases, it is convenient to use Cairo.get_source to get access to the pattern that cairo creates implicitly. For example:

Cairo.set_source_surface cr image x y;
Cairo.Pattern.set_filter (Cairo.get_source cr) Cairo.Pattern.NEAREST;

val get_filter : 'a t -> filter

Gets the current filter for a pattern. See Cairo.Pattern.filter for details on each filter.

val set_matrix : 'a t -> Matrix.t -> unit

Sets the pattern's transformation matrix to matrix. This matrix is a transformation from user space to pattern space.

When a pattern is first created it always has the identity matrix for its transformation matrix, which means that pattern space is initially identical to user space.

Important: Please note that the direction of this transformation matrix is from user space to pattern space. This means that if you imagine the flow from a pattern to user space (and on to device space), then coordinates in that flow will be transformed by the inverse of the pattern matrix.

For example, if you want to make a pattern appear twice as large as it does by default the correct code to use is:

let matrix = Cairo.Matrix.init_scale 0.5 0.5 in
Cairo.Pattern.set_matrix pattern matrix;

val get_matrix : 'a t -> Matrix.t

Returns the pattern's transformation matrix.

package cairo2