B

Task/Bitmap-Write-a-PPM-file/Lua/bitmap-write-a-ppm-file.lua

@@ -0,0 +1,106 @@
+-- helper function, simulates PHP's array_fill function
+local array_fill = function(vbegin, vend, value)
+    local t = {}
+    for i=vbegin, vend do
+        t[i] = value
+    end
+    return t
+end
+
+Bitmap = {}
+Bitmap.__index = Bitmap
+
+function Bitmap.new(width, height)
+    local self = {}
+    setmetatable(self, Bitmap)
+    local white = array_fill(0, width, {255, 255, 255})
+    self.data = array_fill(0, height, white)
+    self.width = width
+    self.height = height
+    return self
+end
+
+function Bitmap:writeRawPixel(file, c)
+    local dt
+    dt = string.format("%c", c)
+    file:write(dt)
+end
+
+function Bitmap:writeComment(fh, ...)
+    local strings = {...}
+    local str = ""
+    local result
+    for _, s in pairs(strings) do
+        str = str .. tostring(s)
+    end
+    result = string.format("# %s\n", str)
+    fh:write(result)
+end
+
+function Bitmap:writeP6(filename)
+    local fh = io.open(filename, 'w')
+    if not fh then
+        error(string.format("failed to open %q for writing", filename))
+    else
+        fh:write(string.format("P6 %d %d 255\n", self.width, self.height))
+        self:writeComment(fh, "automatically generated at ", os.date())
+        for _, row in pairs(self.data) do
+            for _, pixel in pairs(row) do
+                self:writeRawPixel(fh, pixel[1])
+                self:writeRawPixel(fh, pixel[2])
+                self:writeRawPixel(fh, pixel[3])
+            end
+        end
+    end
+end
+
+function Bitmap:fill(x, y, width, heigth, color)
+    width = (width == nil) and self.width or width
+    height = (height == nil) and self.height or height
+    width = width + x
+    height = height + y
+    for i=y, height do
+        for j=x, width do
+            self:setPixel(j, i, color)
+        end
+    end
+end
+
+function Bitmap:setPixel(x, y, color)
+    if x >= self.width then
+        --error("x is bigger than self.width!")
+        return false
+    elseif x < 0 then
+        --error("x is smaller than 0!")
+        return false
+    elseif y >= self.height then
+        --error("y is bigger than self.height!")
+        return false
+    elseif y < 0 then
+        --error("y is smaller than 0!")
+        return false
+    end
+    self.data[y][x] = color
+    return true
+end
+
+function example_colorful_stripes()
+    local w = 260*2
+    local h = 260*2
+    local b = Bitmap.new(w, h)
+    --b:fill(2, 2, 18, 18, {240,240,240})
+    b:setPixel(0, 15, {255,68,0})
+    for i=1, w do
+        for j=1, h do
+            b:setPixel(i, j, {
+                    (i + j * 8) % 256,
+                    (j + (255 * i)) % 256,
+                    (i * j) % 256
+                }
+            );
+        end
+    end
+    return b
+end
+
+example_colorful_stripes():writeP6('p6.ppm')