gamnit: intro custom textures, built programmatically pixel per pixel

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/gamnit/textures.nit b/lib/gamnit/textures.nit
index df3e0b6..271e688 100644 (file)
--- a/lib/gamnit/textures.nit
+++ b/lib/gamnit/textures.nit
@@ -113,6 +113,64 @@ class CheckerTexture
        end
 end
 
+# Custom texture with pixel values filled programmatically
+#
+# At creation, the texture is composed of `width` by `height` (rounded down)
+# transparent pixels. The pixels value can be set using `[]=`.
+#
+# ~~~
+# # Build a texture with 4 colors
+# var tex = new CustomTexture(2.0, 2.0)
+# tex[0, 0] = [1.0, 0.0, 0.0] # Red
+# tex[0, 1] = [0.0, 1.0, 0.0] # Green
+# tex[1, 0] = [0.0, 0.0, 1.0] # Blue
+# tex[1, 1] = [1.0, 1.0, 1.0, 0.5] # Transparent white
+# tex.load
+# ~~~
+class CustomTexture
+       super RootTexture
+
+       redef var width
+       redef var height
+
+       private var cpixels = new CByteArray(4*width.to_i*height.to_i) is lazy
+
+       # Set the `color` of the pixel at `x`, `y` (from the top-left corner)
+       #
+       # The argument `color` should be an array of up to 4 floats (RGBA).
+       # If `color` has less than 4 items, the missing items are replaced by 1.0.
+       #
+       # Require: `not loaded and x < width.to_i and y < height.to_i`
+       fun []=(x, y: Int, color: Array[Float])
+       do
+               assert not loaded else print_error "{class_name}::[]= already loaded"
+               assert x < width.to_i and y < height.to_i else print_error "{class_name}::[] out of bounds"
+
+               # Simple conversion from [0.0..1.0] to [0..255]
+               var bytes = [for c in color do (c*255.0).round.to_i.clamp(0, 255).to_bytes.last]
+               while bytes.length < 4 do bytes.add 255u8
+
+               var offset = 4*(x + y*width.to_i)
+               for i in [0..4[ do cpixels[offset+i] = bytes[i]
+       end
+
+       redef fun load(force)
+       do
+               if loaded then return
+
+               # Round down the desired dimension
+               var width = width.to_i
+               var height = height.to_i
+               self.width = width.to_f
+               self.height = height.to_f
+
+               load_from_pixels(cpixels.native_array, width, height, gl_RGBA)
+
+               cpixels.destroy
+               loaded = true
+       end
+end
+
 # Texture with its own pixels
 class RootTexture
        super Texture