Safe Haskell | None |
---|

Curves is an easy to use library for creating images. The basic
primitive is a curve, which, in the simplest case, is a continuous function
from a `Scalar`

parameter to a 2-dimensional `Point`

on the `curve`

. Images
are rendered (`renderImage`

) as PNG images.

- module Graphics.Curves.Math
- module Graphics.Curves.Colour
- data Image
- point :: Point -> Image
- line :: Point -> Point -> Image
- lineStrip :: [Point] -> Image
- poly :: [Point] -> Image
- circle :: Point -> Scalar -> Image
- circleSegment :: Point -> Scalar -> Scalar -> Scalar -> Image
- curve :: Scalar -> Scalar -> (Scalar -> Point) -> Image
- curve_ :: (Scalar -> Point) -> Image
- curve' :: Transformable a => Scalar -> Scalar -> (Scalar -> a) -> (Scalar -> a -> Point) -> Image
- bSpline :: [Point] -> Image
- bSpline' :: [Point] -> Image
- closedBSpline :: [Point] -> Image
- bezier :: [Point] -> Image
- bezierSegment :: [Point] -> Image
- reverseImage :: Image -> Image
- (+++) :: Image -> Image -> Image
- (+.+) :: Image -> Image -> Image
- (<++) :: Point -> Image -> Image
- (++>) :: Image -> Point -> Image
- differentiate :: Image -> Image
- mapImage :: (Scalar -> Point -> Point) -> Image -> Image
- zipImage :: (Scalar -> Point -> Point -> Point) -> Image -> Image -> Image
- transformImage :: (forall a. Transformable a => Scalar -> a -> a) -> Image -> Image
- curveLength :: Scalar -> Image -> Scalar
- freezeImageSize :: Point -> Image -> Image
- freezeImageOrientation :: Point -> Image -> Image
- freezeImage :: Point -> Image -> Image
- freezeImageStyle :: Image -> Image
- unfreezeImage :: Image -> Image
- type BlendFunc = Maybe Colour -> Maybe Colour -> Maybe Colour
- combine :: BlendFunc -> Image -> Image -> Image
- mapColour :: (Colour -> Colour) -> Image -> Image
- unionBlend :: BlendFunc
- intersectBlend :: BlendFunc
- diffBlend :: BlendFunc
- (<>) :: Monoid m => m -> m -> m
- (><) :: Image -> Image -> Image
- (<->) :: Image -> Image -> Image
- imageBounds :: Image -> Segment
- sampleImage :: Image -> Scalar -> [[Point]]
- module Graphics.Curves.Attribute
- module Graphics.Curves.Style
- autoFit :: Point -> Point -> Image -> Image
- autoStretch :: Point -> Point -> Image -> Image
- renderImage :: FilePath -> Int -> Int -> Colour -> Image -> IO ()
- version :: String

# Documentation

module Graphics.Curves.Math

module Graphics.Curves.Colour

# Image

The image type.

## Curves

lineStrip :: [Point] -> ImageSource

A connected sequence of straight lines. The list must have at least two elements.

circleSegment :: Point -> Scalar -> Scalar -> Scalar -> ImageSource

A circle segment. The third and fourth arguments are the start and end
angle of the segment. If the start angle is bigger than the end angle it's
the clockwise segment, otherwise the counterclockwise segment. For instance,
`circleSegment 0 1 0 pi`

is the top half circle starting in `unitX`

and
ending in `-`

, whereas `unitX`

`circleSegment 0 1 0 (-pi)`

is the bottow
half circle with the same start and end points.

## Advanced curves

curve :: Scalar -> Scalar -> (Scalar -> Point) -> ImageSource

A simple curve whose points are given by the function argument. The first two arguments specify the range of the function. The function must be continuous on this interval.

For example, a straight line between points `p`

and `q`

can be implemented as

`curve 0 1 (``interpolate`

p q)

curve' :: Transformable a => Scalar -> Scalar -> (Scalar -> a) -> (Scalar -> a -> Point) -> ImageSource

The most general form of curve. The curve function is split in two, one
function from the parameter to an arbitrary `Transformable`

object, and a
second function from this object (and the parameter value) to a point on
the curve. The power of this combinator comes from the fact that
transformations (e.g. `translate`

, `scale`

, `rotate`

) of the curve apply
only to the (result of the) first function. This means that the points
computed by the second function are measured in pixels of the final image.

For an example, see the `arrow`

combinator,
which uses a line `Segment`

as the intermediate type and computes the
arrow head in the second function, to ensure that the arrow head has the
same dimensions regardless of how the arrow is scaled.

bSpline :: [Point] -> ImageSource

A uniform cubic B-spline with the given control points.

bSpline' :: [Point] -> ImageSource

A B-spline which starts in the first control point and ends in the last control point. This is achieved by adding two extra copies of the first and last points.

closedBSpline :: [Point] -> ImageSource

A closed B-spline.

closedBSpline ps = bSpline (ps ++ take 3 ps)

bezierSegment :: [Point] -> ImageSource

A Bézier curve of degree n with the given control points `[p0 .. pn]`

.

## Operating on curves

reverseImage :: Image -> ImageSource

Reverse the direction of all curves in an image. Useful in conjunction
with `+++`

.

(+++) :: Image -> Image -> ImageSource

Join the right-most curve of the first image to the left-most curve of the
second image. The `Style`

is inherited from the
curve of the first image. If the end point of the first curve does not
coincide with the starting point of the second curve a straight line is
added to connect the two. This combinator is useful when using
parameterized line styles (such as `dashed`

).

differentiate :: Image -> ImageSource

Differentiating the curves of an image

mapImage :: (Scalar -> Point -> Point) -> Image -> ImageSource

Apply a function to all points of an image. The function also gets the
curve parameter (between 0 and 1) of the given point. This applies after
all transformations so the points are measured in pixels, unless the image
is later unfrozen with `unfreezeImage`

.

transformImage :: (forall a. Transformable a => Scalar -> a -> a) -> Image -> ImageSource

Apply a transformation to an image. Unlike `mapImage`

the transformation
is applied immediately.

curveLength :: Scalar -> Image -> ScalarSource

Compute the length of the curves of an image by approximating it by a series of straight-line segments, each no longer than specified by the first argument.

## Advanced image manipulation

freezeImageSize :: Point -> Image -> ImageSource

Freeze the size of an image around the given point. Scaling the image will only affect the position of the image, not the size. Translation and rotation affect the image normally.

`scaleFrom`

p (`diag`

k) (freezeImageSize p i) == freezeImageSize p i

Scaling with non-uniform scale factors will still distort the image, however.

freezeImageOrientation :: Point -> Image -> ImageSource

Freeze image orientation. Rotations of the image will only affect the position of the image, not its orientation. Translation and scaling affect the image normally.

`rotateAround`

p a (freezeImageOrientation p i) == freezeImageOrientation p i

freezeImage :: Point -> Image -> ImageSource

Freeze both the size and the orientation of an image.

freezeImage p i ==`freezeImageSize`

p i (`freezeImageOrientation`

p i)

freezeImageStyle :: Image -> ImageSource

Freeze the line style of an image. This means that the pixel parameters (distance along the curve and pixel position) are given as they are at this moment, and won't be affected by later transformations.

unfreezeImage :: Image -> ImageSource

Unfreeze an image. After unfreezing any frozen features will be affected by transformations again.

## Combining images

type BlendFunc = Maybe Colour -> Maybe Colour -> Maybe ColourSource

A blend function is used to compute the resulting colour when `combine`

ing
two images.

combine :: BlendFunc -> Image -> Image -> ImageSource

Combine two images using the specified blend function.

Alpha `blend`

the first colour on top of the second colour.

intersectBlend :: BlendFuncSource

The alpha value of the result is the product of the alpha values of the two inputs.

Multiplies the alpha value of the first colour by 1 - the alpha value of the second colour.

(<->) :: Image -> Image -> ImageSource

Subtract the second image from the first.

(<->) = combine diffBlend

## Query functions

imageBounds :: Image -> SegmentSource

Compute the bounds of an image, returning a line segment from the bottom
left corner to the top right corner of the bounding box. This function
ignores line widths. Note that using pixel based features (for instance,
produced by `freezeImageSize`

) means that the bounds may become invalid if
the image is scaled.

sampleImage :: Image -> Scalar -> [[Point]]Source

# Image attributes

Image attributes control things like the colour and width of curves.

module Graphics.Curves.Attribute

module Graphics.Curves.Style

# Rendering

autoFit :: Point -> Point -> Image -> ImageSource

Scale the an image to fit inside the the box given by the two points (bottom-left and top-right corners).

autoStretch :: Point -> Point -> Image -> ImageSource

Scale the an image to fit inside the the box given by the two points (bottom-left and top-right corners). Does not preserve aspect ratio.

:: FilePath | File in which to store the image |

-> Int | Image width |

-> Int | Image height |

-> Colour | Background colour |

-> Image | Image to render |

-> IO () |

Render an image as a PNG file with a 1-bit alpha channel. Semi-transparent pixels in the image are blended with the given background colour to produce opaque pixels.