Tsukina-7mochi · Tsukina-7mochi · Nov 14, 2025 · Nov 14, 2025 · Nov 14, 2025 · Nov 14, 2025
diff --git a/src/pkg/asepriteUtil/mock.lua b/src/pkg/asepriteUtil/mock.lua
@@ -0,0 +1,85 @@
+---Mock implementations of Aseprite APIs for testing
+
+---Mock ColorMode enum
+---@class ColorMode
+local ColorMode = {
+    RGB = 0,
+    GRAY = 1,
+    INDEXED = 2,
+}
+
+---Mock app.pixelColor API
+---RGBA format: R=bits[0-7], G=bits[8-15], B=bits[16-23], A=bits[24-31]
+local pixelColor = {
+    ---Constructs a 32-bit RGBA pixel value
+    ---@param r integer Red component (0-255)
+    ---@param g integer Green component (0-255)
+    ---@param b integer Blue component (0-255)
+    ---@param a? integer Alpha component (0-255), defaults to 255
+    ---@return integer
+    rgba = function (r, g, b, a)
+        a = a or 255
+        return r | (g << 8) | (b << 16) | (a << 24)
+    end,
+
+    ---Extracts red component from RGBA pixel
+    ---@param pixel integer
+    ---@return integer
+    rgbaR = function (pixel)
+        return pixel & 0xFF
+    end,
+
+    ---Extracts green component from RGBA pixel
+    ---@param pixel integer
+    ---@return integer
+    rgbaG = function (pixel)
+        return (pixel >> 8) & 0xFF
+    end,
+
+    ---Extracts blue component from RGBA pixel
+    ---@param pixel integer
+    ---@return integer
+    rgbaB = function (pixel)
+        return (pixel >> 16) & 0xFF
+    end,
+
+    ---Extracts alpha component from RGBA pixel
+    ---@param pixel integer
+    ---@return integer
+    rgbaA = function (pixel)
+        return (pixel >> 24) & 0xFF
+    end,
+}
+
+---Mock app object
+local app = {
+    pixelColor = pixelColor,
+}
+
+---Creates a mock Image object for testing
+---@param width integer Image width in pixels
+---@param height integer Image height in pixels
+---@param pixelData integer[] Array of RGBA pixel values (length = width * height)
+---@return table Mock Image object
+local function createImage (width, height, pixelData)
+    return {
+        width = width,
+        height = height,
+        colorMode = ColorMode.RGB,
+        bytesPerPixel = 4,
+        rowStride = width * 4,
+        ---Gets pixel at x,y coordinates
+        ---@param x integer
+        ---@param y integer
+        ---@return integer
+        getPixel = function (self, x, y)
+            return pixelData[y * width + x + 1]
+        end,
+    }
+end
+
+return {
+    ColorMode = ColorMode,
+    app = app,
+    createImage = createImage,
+}
diff --git a/src/pkg/bitmap/bitmap_test.lua b/src/pkg/bitmap/bitmap_test.lua
@@ -0,0 +1,217 @@
+local describe = require("lib.test").describe
+local expect = require("lib.test").expect
+local test = require("lib.test").test
+
+-- Set up mocks
+local mock = require("pkg.asepriteUtil.mock")
+_G.ColorMode = mock.ColorMode
+_G.app = mock.app
+
+local bitmap = require("pkg.bitmap")
+
+describe("bitmap", function ()
+    describe("create", function ()
+        test("creates valid BMP file header", function ()
+            -- 1x1 red pixel
+            local pixels = { 0x000000FF } -- RGBA: red=255, green=0, blue=0, alpha=0
+            local image = mock.createImage(1, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- Check BMP signature
+            expect(bmp:sub(1, 2)):toBe("BM")
+
+            -- File size: 54 (headers) + 4 (1 pixel * 3 bytes + 1 padding) = 58
+            expect(bmp:sub(3, 6)):toBe("\x3A\x00\x00\x00")
+
+            -- Reserved
+            expect(bmp:sub(7, 10)):toBe("\x00\x00\x00\x00")
+
+            -- Data offset should be 54
+            expect(bmp:sub(11, 14)):toBe("\x36\x00\x00\x00")
+        end)
+
+        test("creates valid bitmap info header", function ()
+            local pixels = { 0x00000000 } -- Black pixel
+            local image = mock.createImage(1, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- Info header starts at byte 15
+            -- Header size = 40
+            expect(bmp:sub(15, 18)):toBe("\x28\x00\x00\x00")
+
+            -- Width = 1
+            expect(bmp:sub(19, 22)):toBe("\x01\x00\x00\x00")
+
+            -- Height = 1
+            expect(bmp:sub(23, 26)):toBe("\x01\x00\x00\x00")
+
+            -- Planes = 1
+            expect(bmp:sub(27, 28)):toBe("\x01\x00")
+
+            -- Bits per pixel = 24
+            expect(bmp:sub(29, 30)):toBe("\x18\x00")
+        end)
+
+        test("encodes pixels in BGR order", function ()
+            -- Create a 1x1 image with red pixel (R=255, G=0, B=0)
+            local pixels = { 0x000000FF }
+            local image = mock.createImage(1, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- Pixel data starts at byte 55 (after 54-byte header)
+            -- BGR order: B=0, G=0, R=255
+            expect(bmp:sub(55, 57)):toBe("\x00\x00\xFF")
+        end)
+
+        test("adds correct row padding for width=1", function ()
+            local pixels = { 0x00000000 }
+            local image = mock.createImage(1, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- 1 pixel = 3 bytes, needs 1 byte padding to reach 4
+            -- Pixel data: 3 bytes + 1 padding = 4 bytes total
+            expect(#bmp):toBe(58)
+            expect(bmp:sub(58, 58)):toBe("\x00") -- Padding byte
+        end)
+
+        test("adds correct row padding for width=2", function ()
+            local pixels = { 0x00000000, 0x00000000 }
+            local image = mock.createImage(2, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- 2 pixels = 6 bytes, needs 2 bytes padding to reach 8
+            expect(#bmp):toBe(62) -- 54 + 8
+        end)
+
+        test("adds no padding for width=4", function ()
+            local pixels = {
+                0x00000000,
+                0x00000000,
+                0x00000000,
+                0x00000000,
+            }
+            local image = mock.createImage(4, 1, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- 4 pixels = 12 bytes, already aligned to 4, no padding needed
+            expect(#bmp):toBe(66) -- 54 + 12
+        end)
+
+        test("stores rows bottom-to-top", function ()
+            -- Create a 2x2 image:
+            -- Top row (y=0):    Red(255,0,0)    Green(0,255,0)
+            -- Bottom row (y=1): Blue(0,0,255)   White(255,255,255)
+            local pixels = {
+                0x000000FF, -- Top-left: Red
+                0x0000FF00, -- Top-right: Green
+                0x00FF0000, -- Bottom-left: Blue
+                0x00FFFFFF, -- Bottom-right: White
+            }
+            local image = mock.createImage(2, 2, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- Pixel data starts at byte 55
+            -- First row in BMP should be bottom row (y=1): Blue, White
+            -- Blue in BGR: B=255, G=0, R=0
+            expect(bmp:sub(55, 57)):toBe("\xFF\x00\x00")
+
+            -- White in BGR: B=255, G=255, R=255
+            expect(bmp:sub(58, 60)):toBe("\xFF\xFF\xFF")
+
+            -- 2 pixels = 6 bytes, need 2 bytes padding
+            expect(bmp:sub(61, 62)):toBe("\x00\x00")
+
+            -- Second row in BMP should be top row (y=0): Red, Green
+            -- Red in BGR: B=0, G=0, R=255
+            expect(bmp:sub(63, 65)):toBe("\x00\x00\xFF")
+
+            -- Green in BGR: B=0, G=255, R=0
+            expect(bmp:sub(66, 68)):toBe("\x00\xFF\x00")
+        end)
+
+        test("handles 3x3 image correctly", function ()
+            -- Create a simple 3x3 image with all black pixels
+            local pixels = {}
+            for i = 1, 9 do
+                pixels[i] = 0x00000000
+            end
+            local image = mock.createImage(3, 3, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- 3 pixels per row = 9 bytes, needs 3 bytes padding to reach 12
+            -- Total pixel data = (9 + 3) * 3 rows = 36 bytes
+            expect(#bmp):toBe(90) -- 54 + 36
+        end)
+
+        test("throws error for non-RGB image", function ()
+            local image = {
+                width = 1,
+                height = 1,
+                colorMode = mock.ColorMode.GRAY,
+                getPixel = function ()
+                    return 0
+                end,
+            }
+
+            local success, err = pcall(function ()
+                bitmap.create(image)
+            end)
+
+            expect(success):toBe(false)
+            expect(err:find("RGB")):toBeTruthy()
+        end)
+
+        test("creates complete valid 2x2 BMP", function ()
+            -- Create a simple 2x2 test pattern
+            local pixels = {
+                0x000000FF, -- Red
+                0x0000FF00, -- Green
+                0x00FF0000, -- Blue
+                0x0000FFFF, -- Yellow
+            }
+            local image = mock.createImage(2, 2, pixels)
+            local bmp = tostring(bitmap.create(image))
+
+            -- Verify it's a complete BMP file
+            expect(bmp:sub(1, 2)):toBe("BM")
+            expect(#bmp):toBe(70) -- 54 + (6 bytes pixels + 2 padding) * 2 rows
+        end)
+
+        test("BitmapFile has correct structure", function ()
+            local pixels = { 0x00000000 }
+            local image = mock.createImage(1, 1, pixels)
+            local bmpFile = bitmap.create(image)
+
+            -- Check that BitmapFile has the expected fields
+            expect(type(bmpFile.fileHeader)):toBe("string")
+            expect(type(bmpFile.bitmapInfoHeader)):toBe("string")
+            expect(type(bmpFile.pixelData)):toBe("string")
+
+            -- File header should be 14 bytes
+            expect(#bmpFile.fileHeader):toBe(14)
+
+            -- Bitmap info header should be 40 bytes
+            expect(#bmpFile.bitmapInfoHeader):toBe(40)
+
+            -- Pixel data should be 4 bytes (3 + 1 padding)
+            expect(#bmpFile.pixelData):toBe(4)
+        end)
+
+        test("tostring method works", function ()
+            local pixels = { 0x00000000 }
+            local image = mock.createImage(1, 1, pixels)
+            local bmpFile = bitmap.create(image)
+
+            -- Test explicit tostring method
+            local str1 = bmpFile:tostring()
+            expect(str1:sub(1, 2)):toBe("BM")
+
+            -- Test implicit __tostring metamethod
+            local str2 = tostring(bmpFile)
+            expect(str2:sub(1, 2)):toBe("BM")
+
+            -- Both should produce the same result
+            expect(str1):toBe(str2)
+        end)
+    end)
+end)