Simplify and refactor code, improve performance

[tga_encoder.git] / init.lua

diff --git a/init.lua b/init.lua
index 0a831ca94ec0f5ef888b70a266ccc3c40ed32303..96afda5e131ca4eb9a9f6adda339fef1f3182524 100644 (file)
--- a/init.lua
+++ b/init.lua
@@ -1,11 +1,78 @@
 tga_encoder = {}
 
-function tga_encoder.encode_pixels(pixels)
+local image = setmetatable({}, {
+       __call = function(self, ...)
+               local t = setmetatable({}, {__index = self})
+               t:constructor(...)
+               return t
+       end,
+})
+
+function image:constructor(pixels)
+       self.data = ""
+       self.pixels = pixels
+       self.width = #pixels[1]
+       self.height = #pixels
+
+       self:encode()
+end
+
+function image:encode_colormap_spec()
+       self.data = self.data
+               .. string.char(0, 0) -- first entry index
+               .. string.char(0, 0) -- number of entries
+               .. string.char(0) -- bits per pixel
+end
+
+function image:encode_image_spec()
+       self.data = self.data
+               .. string.char(0, 0) -- X-origin
+               .. string.char(0, 0) -- Y-origin
+               .. string.char(self.width  % 256, math.floor(self.width  / 256)) -- width
+               .. string.char(self.height % 256, math.floor(self.height / 256)) -- height
+               .. string.char(24) -- pixel depth (RGB = 3 bytes = 24 bits)
+               .. string.char(0) -- image descriptor
+end
+
+function image:encode_header()
+       self.data = self.data
+               .. string.char(0) -- image id
+               .. string.char(0) -- color map type
+               .. string.char(2) -- image type (uncompressed true-color image = 2)
+       self:encode_colormap_spec() -- color map specification
+       self:encode_image_spec() -- image specification
 end
 
-function tga_encoder.save_image(filename, pixels)
-       local f = assert(io.open(filename))
-       local encoded = tga_encoder.encode_pixels(pixels)
-       f:write(encoded)
+function image:encode_data()
+       for _, row in ipairs(self.pixels) do
+               for _, pixel in ipairs(row) do
+                       self.data = self.data
+                               .. string.char(pixel[3], pixel[2], pixel[1])
+               end
+       end
+end
+
+function image:encode_footer()
+       self.data = self.data
+               .. string.char(0, 0, 0, 0) -- extension area offset
+               .. string.char(0, 0, 0, 0) -- developer area offset
+               .. "TRUEVISION-XFILE"
+               .. "."
+               .. string.char(0)
+end
+
+function image:encode()
+       self:encode_header() -- header
+       -- no color map and image id data
+       self:encode_data() -- encode data
+       -- no extension or developer area
+       self:encode_footer() -- footer
+end
+
+function image:save(filename)
+       local f = assert(io.open(filename, "w"))
+       f:write(self.data)
        f:close()
 end
+
+tga_encoder.image = image