Haskell draw image over image - haskell

Question

I want to take two different images (taken from image files, like .png) and draw one over the other several times in different positions. The resulting image should be presented on screen or generate a new image file, whichever is easier. I´ll be taking that new image and drawing on it more with further operations
Is there any Haskell library that allows me to do this?

Answer 1

You can use JuicyPixels to do that sort of thing:
module Triangles where
import Codec.Picture
import LineGraphics
{-| Parameterize color smoothly as a function of angle -}
colorWheel :: Float -> Colour
colorWheel x = (r, g, b, a)
where
r = floor $ (cos x + 1) * (255 / 2)
g = floor $ (sin x + 1) * (255 / 2)
b = floor $ (cos (x+(pi/2)) + 1) * (255 / 2)
a = 255
{-| Draw a triangle centered about the point (x, y) -}
triangle :: Point -> Path
triangle (x, y) =
[ (x - k, y - k)
, (x + k, y - k)
, (x, y + k)
, (x - k, y - k)
]
where
size = 30
k = size / 2
{-|
Draw 'n' equally-spaced triangles at a radius of 'r' about a center
point, '(x, y)'.
-}
triangles :: Float -> Radius -> Vector -> Picture
triangles n r (x, y) =
[ (colorWheel theta, tri theta) | theta <- steps n ]
where
tri theta = triangle ((r * cos theta) + x, (r * sin theta) + y)
{-| Interpolate the range [0, 2pi] by 'n' steps -}
steps :: Float -> [Float]
steps n = map (\i -> i * (2*pi/n)) [0 .. n]
And we'll use this module of supporting code:
module LineGraphics (
Point, Vector, Line, Path, Picture, Colour, Radius,
black,
drawPicture,
) where
import Graphics.Rasterific hiding (Point, Vector, Line, Path, polygon)
import Graphics.Rasterific.Texture
import Codec.Picture
type Radius = Float
type Point = (Float, Float)
type Vector = (Float, Float)
type Line = (Point, Point)
type Path = [Point]
type Picture = [(Colour, Path)]
type Colour = (Int, Int, Int, Int) -- red, green, blue, opacity
black = (0, 0, 0, 255)
drawPicture :: Float -> Picture -> Image PixelRGBA8
drawPicture linewidth picture =
renderDrawing 800 800 (toColour black) $
mapM_ renderFn picture
where
renderFn (col, path) = withTexture (uniformTexture $ toColour col) (drawPath path)
drawPath points = stroke linewidth JoinRound (CapRound, CapStraight 0) $
polyline (map (\(x, y) -> V2 x y) points)
toColour (a,b,c,d) = PixelRGBA8
(fromIntegral a) (fromIntegral b) (fromIntegral c) (fromIntegral d)
And here's what we get: