doc what i can doc

Author: sevenrats

source/utils/fakeBlurhash.brs

@@ -6,6 +6,7 @@
 import "pkg:/source/utils/config.brs"
 import "pkg:/source/utils/librokudev.brs"
 
+' construct a bmp by hand in hex to avoid drawing
 function bitmapImageByteArray(numX as integer, numY as integer, pixels)
     bmp = "424D4C000000000000001A0000000C000000"
     bmp = bmp + rdINTtoHEX(numX) + "00" + rdINTtoHEX(numY) + "0001001800"
@@ -37,7 +38,6 @@ function decode83(str as string) as integer
 end function
 
 function isBlurhashValid(blurhash as string) as boolean
-
     if blurhash = invalid or len(blurhash) < 6
         print "The blurhash string must be at least 6 characters"
         return false
@@ -113,17 +113,25 @@ function linearTosRGB(value as float)
     end if
 end function
 
+' this function takes a blurhash, a dimensions in terms of elements,
+' renders the blurhash using the fake-blurhash decoding algorithm
+' then returns a filesystem uri pointing at the file
+' the images in the fs are named with a hash of the blurhash string
+' so that items which already exist are not rendered twice
 function renderFakeBlurhash(blurhash as string, width as integer, height as integer, punch = 1 as float)
-    bhfn = CreateObject("roByteArray")
-    bhfn.FromAsciiString(blurhash)
+    ' determine the file name
+    ' create the hasher and the bytestring for the hasher
+    blurhashByteArray = CreateObject("roByteArray")
+    blurhashByteArray.FromAsciiString(blurhash)
     digest = CreateObject("roEVPDigest")
     digest.Setup("md5")
-    digest.Update(bhfn)
-    fn = digest.Final()
+    digest.Update(blurhashByteArray)
+    filename = digest.Final()
     localFileSystem = CreateObject("roFileSystem")
-    if localFileSystem.Exists("tmp://" + fn + ".bmp")
-        return "tmp://" + fn + ".bmp"
+    if localFileSystem.Exists("tmp://" + filename + ".bmp")
+        return "tmp://" + filename + ".bmp"
     end if
+    ' doesn't exist in fs. render it.
     if isBlurhashValid(blurhash) = false then return invalid
     sizeFlag = decode83(Mid(blurhash, 1, 1))
     numY = Fix(sizeFlag / 9) + 1
@@ -169,6 +177,6 @@ function renderFakeBlurhash(blurhash as string, width as integer, height as inte
         pixels.push(pixel)
     end for
     ba = bitmapImageByteArray(numX, numY, pixels)
-    ba.WriteFile("tmp://" + fn + ".bmp")
-    return "tmp://" + fn + ".bmp"
+    ba.WriteFile("tmp://" + filename + ".bmp")
+    return "tmp://" + filename + ".bmp"
 end function