Add usage examples

README.md

@@ -2,3 +2,5 @@
 A TGA Encoder written in Lua without the use of external Libraries.
 
 May be used as a Minetest mod.
+
+See `examples.lua` for example code and usage hints.

examples.lua

@@ -0,0 +1,49 @@
+dofile("init.lua")
+
+-- encode a bitmap
+local _ = { 0, 0, 0 }
+local R = { 255, 127, 127 }
+local pixels = {
+	{ _, _, _, _, _, _, _ },
+	{ _, _, _, R, _, _, _ },
+	{ _, _, R, R, R, _, _ },
+	{ _, R, R, R, R, R, _ },
+	{ _, R, R, R, R, R, _ },
+	{ _, _, R, _, R, _, _ },
+	{ _, _, _, _, _, _, _ },
+}
+tga_encoder.image(pixels):save("bitmap_small.tga")
+
+-- change a single pixel, then rescale the bitmap
+local pixels_orig = pixels
+pixels_orig[4][4] = { 255, 255, 255 }
+local pixels = {}
+for x = 1,56,1 do
+	local x_orig = math.ceil(x/8)
+	for z = 1,56,1 do
+		local z_orig = math.ceil(z/8)
+		local color = pixels_orig[z_orig][x_orig]
+		pixels[z] = pixels[z] or {}
+		pixels[z][x] = color
+	end
+end
+tga_encoder.image(pixels):save("bitmap_large.tga")
+
+local pixels = {}
+for x = 1,16,1 do -- left to right
+	for z = 1,16,1 do -- bottom to top
+		local r = math.min(x * 32 - 1, 255)
+		local g = math.min(z * 32 - 1, 255)
+		local b = 0
+		-- blue rectangle in top right corner
+		if x > 8 and z > 8 then
+			r = 0
+			g = 0
+			b = math.min(z * 16 - 1, 255)
+		end
+		local color = { r, g, b }
+		pixels[z] = pixels[z] or {}
+		pixels[z][x] = color
+	end
+end
+tga_encoder.image(pixels):save("gradients.tga")