Move encoding format heuristics from image:save() to image:encode()

examples.lua

@@ -14,6 +14,22 @@ local pixels = {
 }
 tga_encoder.image(pixels):save("bitmap_small.tga")
 
+-- test that image can be encoded
+local bitmap_small_0 = tga_encoder.image(pixels)
+bitmap_small_0:encode()
+assert(191 == #bitmap_small_0.data)
+
+-- test that imbage can be encoded with parameters
+local bitmap_small_1 = tga_encoder.image(pixels)
+bitmap_small_1:encode(
+	{
+		colormap = {},
+		color_format = "B8G8R8",
+		compression = "RAW",
+	}
+)
+assert(191 == #bitmap_small_1.data)
+
 -- change a single pixel, then rescale the bitmap
 local pixels_orig = pixels
 pixels_orig[4][4] = { 255, 255, 255 }

init.lua

@@ -549,15 +549,6 @@ function image:encode_footer()
 end
 
 function image:encode(properties)
-	self.data = ""
-	self:encode_header(properties) -- header
-	-- no color map and image id data
-	self:encode_data(properties) -- encode data
-	-- no extension or developer area
-	self:encode_footer() -- footer
-end
-
-function image:save(filename, properties)
 	local properties = properties or {}
 	properties.colormap = properties.colormap or {}
 	properties.compression = properties.compression or "RAW"
@@ -584,6 +575,15 @@ function image:save(filename, properties)
 	end
 	assert( nil ~= properties.color_format )
 
+	self.data = ""
+	self:encode_header(properties) -- header
+	-- no color map and image id data
+	self:encode_data(properties) -- encode data
+	-- no extension or developer area
+	self:encode_footer() -- footer
+end
+
+function image:save(filename, properties)
 	self:encode(properties)
 
 	local f = assert(io.open(filename, "wb"))