X-Git-Url: http://nitlanguage.org

diff --git a/lib/gamnit/textures.nit b/lib/gamnit/textures.nit
index 4bc95cb..4fb98ac 100644
--- a/lib/gamnit/textures.nit
+++ b/lib/gamnit/textures.nit
@@ -80,9 +80,7 @@ abstract class Texture
 	# Prepare a subtexture from this texture, from the given pixel offsets
 	fun subtexture(left, top, width, height: Numeric): Subtexture
 	do
-		# Setup the subtexture
-		var subtex = new Subtexture(root, self, left.to_f, top.to_f, width.to_f, height.to_f)
-		return subtex
+		return new AbsoluteSubtexture(self, left.to_f, top.to_f, width.to_f, height.to_f)
 	end
 
 	# Offset of the left border on `root` from 0.0 to 1.0
@@ -210,7 +208,7 @@ class CustomTexture
 	end
 end
 
-# Texture with its own pixels
+# Texture with its own pixel data
 class RootTexture
 	super Texture
 
@@ -223,6 +221,18 @@ class RootTexture
 
 	init do all_root_textures.add self
 
+	# Should the pixels RGB values be premultiplied by their alpha value at loading?
+	#
+	# All gamnit textures must have premultiplied alpha, it provides a better
+	# alpha blending, avoids artifacts and allows for additive blending.
+	#
+	# When at `true`, the default, pixels RGB values are premultiplied
+	# at loading. Set to `false` if pixels RGB values are already
+	# premultiplied in the source data.
+	#
+	# This value must be set before calling `load`.
+	var premultiply_alpha = true is writable
+
 	private fun load_from_pixels(pixels: Pointer, width, height: Int, format: GLPixelFormat)
 	do
 		var max_texture_size = glGetIntegerv(gl_MAX_TEXTURE_SIZE, 0)
@@ -231,6 +241,11 @@ class RootTexture
 			return
 		end
 
+		# Premultiply alpha?
+		if premultiply_alpha and format == gl_RGBA then
+			pixels.premultiply_alpha(width, height)
+		end
+
 		glPixelStorei(gl_UNPACK_ALIGNEMENT, 1)
 		var tex = glGenTextures(1)[0]
 		gl_texture = tex
@@ -240,6 +255,9 @@ class RootTexture
 
 		glHint(gl_GENERATE_MIPMAP_HINT, gl_NICEST)
 		glGenerateMipmap(gl_TEXTURE_2D)
+		glTexParameteri(gl_TEXTURE_2D, gl_TEXTURE_MIN_FILTER, gl_LINEAR_MIPMAP_LINEAR)
+
+		glBindTexture(gl_TEXTURE_2D, 0)
 	end
 
 	private fun load_checker(size: Int)
@@ -309,18 +327,25 @@ class TextureAsset
 end
 
 # Texture derived from another texture, does not own its pixels
-class Subtexture
+abstract class Subtexture
 	super Texture
 
-	redef var root
-
 	# Parent texture, from which this texture was created
 	var parent: Texture
 
-	# Left border of this texture compared to `parent`
+	redef var root = parent.root is lateinit
+
+	redef fun load(force) do root.load(force)
+end
+
+# Subtexture created from pixel coordinates within `parent`
+class AbsoluteSubtexture
+	super Subtexture
+
+	# Left border of this texture relative to `parent`
 	var left: Float
 
-	# Top border of this texture compared to `parent`
+	# Top border of this texture relative to `parent`
 	var top: Float
 
 	private fun set_wh(width, height: Float)
@@ -329,14 +354,25 @@ class Subtexture
 		self.height = height
 	end
 
-	redef fun load(force) do root.load(force)
-
 	redef var offset_left = parent.offset_left + left / root.width is lazy
 	redef var offset_top = parent.offset_top + top / root.height is lazy
 	redef var offset_right = offset_left + width / root.width is lazy
 	redef var offset_bottom = offset_top + height / root.height is lazy
 end
 
+# Subtexture created from relative coordinates ([0..1]) out of the `root` texture
+class RelativeSubtexture
+	super Subtexture
+
+	redef var offset_left
+	redef var offset_top
+	redef var offset_right
+	redef var offset_bottom
+
+	redef fun width do return root.width * (offset_right - offset_left)
+	redef fun height do return root.height * (offset_bottom - offset_top)
+end
+
 redef class Sys
 	# All declared root textures
 	var all_root_textures = new TextureSet
@@ -349,3 +385,20 @@ class TextureSet
 	# Load all texture of this set
 	fun load_all do for t in self do t.load
 end
+
+redef class Pointer
+	# Multiply RBG values by their alpha value
+	private fun premultiply_alpha(width, height: Int) `{
+		uint8_t *bytes = (uint8_t *)self;
+		int x, y, i = 0;
+		for(y = 0; y < height; y ++) {
+			for(x = 0; x < width; x ++) {
+				int a = bytes[i+3];
+				bytes[i  ] = bytes[i  ] * a / 255;
+				bytes[i+1] = bytes[i+1] * a / 255;
+				bytes[i+2] = bytes[i+2] * a / 255;
+				i += 4;
+			}
+		}
+	`}
+end