update tester

.gitignore

@@ -45,3 +45,4 @@ Temporary Items
 *.exe
 nimcache
 bug
+tester/temp.png

nimPNG.nim

@@ -2412,7 +2412,7 @@ proc filterScanLine(output: var cstring, scanLine, prevLine: cstring, len, byteW
       for i in byteWidth..len-1:
         output[i] = chr(scanLine[i].uint - scanLine[i - byteWidth].uint)
   else:
-    raise PNGError("unsupported fitler type")
+    raise PNGError("unsupported filter type")
 
 proc filterZero(output: var cstring, input: cstring, w, h, bpp: int) =
   #the width of a scanline in bytes, not including the filter type

testCodec.nim

@@ -1,4 +1,4 @@
-import nimPNG, streams, math, strutils, tables, base64
+import nimPNG, streams, math, strutils, tables, base64, os
 
 type
   Image = ref object
@@ -979,6 +979,17 @@ proc testAutoColorModels() =
   addColor16(alpha16, 257, 0, 0, 10000)
   testAutoColorModel(alpha16, 16, LCT_RGBA, 16, false)
 
+proc testFilter() =
+  echo "test Filter"
+  let input = "tester" & DirSep & "tfilter.png"
+  let temp = "tester" & DirSep & "temp.png"
+  let png = loadPNG32(input)
+  discard savePNG32(temp, png.data, png.width, png.height)
+  let png2 = loadPNG32(temp)
+  if png.data != png2.data:
+    echo "testFilter failed"
+    quit()
+
 proc doMain() =
   testPNGCodec()
   testPngSuiteTiny()
@@ -990,8 +1001,9 @@ proc doMain() =
   testColorConvert2()
   testPaletteToPaletteConvert()
   testRGBToPaletteConvert()
-  test16bitColorEndianness();
-  testNoAutoConvert();
-  testAutoColorModels();
+  test16bitColorEndianness()
+  testNoAutoConvert()
+  testAutoColorModels()
+  testFilter()
 
 doMain()