Resurrect old nim-native jpeg parser and fix most issues (#414)

* Add new jpeg tests.
* Resurrect old jpeg.
* Fix Jpeg grayscale
* Fix 4:1:1 scaling.
* Better chunk scanner.
* Fight progressive.
* Fight restart markers.
* Jpeg can now parse all of the test files.
* Fuzzing and overflow checks
* Make getBits* the only way to read the bits. 
* Make Quantiziation and IDCT happen only in one place.
* Rename jpg folder to jpeg

.gitignore

@@ -14,3 +14,4 @@ __pycache__
 bindings/generated
 *.dSYM
 dump.txt
+tests/fileformats/jpeg/generated

src/pixie/fileformats/jpg.nim

@@ -1,15 +1,17 @@
 import pixie/common, pixie/images
 
-when defined(pixieUseStb):
-  import pixie/fileformats/stb_image/stb_image
-
 const
   jpgStartOfImage* = [0xFF.uint8, 0xD8]
 
+when defined(pixieUseStb):
+  import pixie/fileformats/stb_image/stb_image
+else:
+  import pixie/fileformats/jpeg
+
 proc decodeJpg*(data: string): Image {.inline, raises: [PixieError].} =
   ## Decodes the JPEG into an Image.
   when not defined(pixieUseStb):
-    raise newException(PixieError, "Decoding JPG requires -d:pixieUseStb")
+    decodeJpeg(data)
   else:
     var
       width: int

tests/all.nim

@@ -5,7 +5,7 @@ import
   test_gif,
   test_images,
   test_images_draw,
-  test_jpg,
+  test_jpeg,
   test_masks,
   test_paints,
   test_paths,

tests/benchmark_jpeg.nim

@@ -1,6 +1,6 @@
 import benchy, pixie/fileformats/jpg
 
-let data = readFile("tests/fileformats/jpg/jpeg420exif.jpg")
+let data = readFile("tests/fileformats/jpeg/jpeg420exif.jpg")
 
 timeIt "pixie decode":
   discard decodeJpg(data)

tests/fuzz_jpeg.nim

@@ -0,0 +1,65 @@
+import pixie/common, pixie/fileformats/jpg, random, strformat
+
+randomize()
+
+var files = @[
+  "tests/fileformats/jpeg/master/red.jpg",
+  "tests/fileformats/jpeg/master/green.jpg",
+  "tests/fileformats/jpeg/master/blue.jpg",
+  "tests/fileformats/jpeg/master/white.jpg",
+  "tests/fileformats/jpeg/master/black.jpg",
+
+  "tests/fileformats/jpeg/master/8x8.jpg",
+  "tests/fileformats/jpeg/master/8x8_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/16x16.jpg",
+  "tests/fileformats/jpeg/master/16x16_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/quality_01.jpg",
+  "tests/fileformats/jpeg/master/quality_10.jpg",
+  "tests/fileformats/jpeg/master/quality_25.jpg",
+  "tests/fileformats/jpeg/master/quality_50.jpg",
+  "tests/fileformats/jpeg/master/quality_100.jpg",
+
+  "tests/fileformats/jpeg/master/cat_4_4_4.jpg",
+  "tests/fileformats/jpeg/master/cat_4_4_4.jpg",
+  "tests/fileformats/jpeg/master/cat_4_2_2.jpg",
+  "tests/fileformats/jpeg/master/cat_4_2_0.jpg",
+  "tests/fileformats/jpeg/master/cat_4_1_1.jpg",
+  "tests/fileformats/jpeg/master/cat_4_4_4_progressive.jpg",
+  "tests/fileformats/jpeg/master/cat_restart_markers_5.jpg",
+  "tests/fileformats/jpeg/master/cat_restart_markers_5_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/mandrill.jpg",
+
+  "tests/fileformats/jpeg/master/exif_overrun.jpg",
+  "tests/fileformats/jpeg/master/grayscale_test.jpg",
+  "tests/fileformats/jpeg/master/progressive.jpg",
+
+  "tests/fileformats/jpeg/master/testimg.jpg",
+  "tests/fileformats/jpeg/master/testimgp.jpg",
+  "tests/fileformats/jpeg/master/testorig.jpg",
+  "tests/fileformats/jpeg/master/testprog.jpg",
+]
+
+for i in 0 ..< 10_000:
+  let original = readFile(sample(files))
+
+  var data = original
+  let
+    pos = rand(0 ..< data.len)
+    value = rand(255).uint8
+  data[pos] = value.char
+  echo &"{i} {pos} {value}"
+
+  try:
+    let img = decodeJpg(data)
+    doAssert img.height > 0 and img.width > 0
+  except PixieError:
+    discard
+  data = data[0 ..< pos]
+  try:
+    let img = decodeJpg(data)
+    doAssert img.height > 0 and img.width > 0
+  except PixieError:
+    discard

tests/fuzz_jpg.nim

@@ -1,25 +0,0 @@
-import pixie/common, pixie/fileformats/jpg, random, strformat
-
-randomize()
-
-let original = cast[seq[uint8]](readFile("tests/fileformats/jpg/jpeg420exif.jpg"))
-
-for i in 0 ..< 10_000:
-  var data = original
-  let
-    pos = rand(data.len)
-    value = rand(255).uint8
-  data[pos] = value
-  echo &"{i} {pos} {value}"
-  try:
-    let img = decodeJpg(data)
-    doAssert img.height > 0 and img.width > 0
-  except PixieError:
-    discard
-
-  data = data[0 ..< pos]
-  try:
-    let img = decodeJpg(data)
-    doAssert img.height > 0 and img.width > 0
-  except PixieError:
-    discard

tests/test_jpeg.nim

@@ -0,0 +1,46 @@
+import pixie, strutils
+
+import pixie/fileformats/jpg
+
+var files = @[
+  "tests/fileformats/jpeg/master/red.jpg",
+  "tests/fileformats/jpeg/master/green.jpg",
+  "tests/fileformats/jpeg/master/blue.jpg",
+  "tests/fileformats/jpeg/master/white.jpg",
+  "tests/fileformats/jpeg/master/black.jpg",
+
+  "tests/fileformats/jpeg/master/8x8.jpg",
+  "tests/fileformats/jpeg/master/8x8_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/16x16.jpg",
+  "tests/fileformats/jpeg/master/16x16_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/quality_01.jpg",
+  "tests/fileformats/jpeg/master/quality_10.jpg",
+  "tests/fileformats/jpeg/master/quality_25.jpg",
+  "tests/fileformats/jpeg/master/quality_50.jpg",
+  "tests/fileformats/jpeg/master/quality_100.jpg",
+
+  "tests/fileformats/jpeg/master/cat_4_4_4.jpg",
+  "tests/fileformats/jpeg/master/cat_4_4_4.jpg",
+  "tests/fileformats/jpeg/master/cat_4_2_2.jpg",
+  "tests/fileformats/jpeg/master/cat_4_2_0.jpg",
+  "tests/fileformats/jpeg/master/cat_4_1_1.jpg",
+  "tests/fileformats/jpeg/master/cat_4_4_4_progressive.jpg",
+  "tests/fileformats/jpeg/master/cat_restart_markers_5.jpg",
+  "tests/fileformats/jpeg/master/cat_restart_markers_5_progressive.jpg",
+
+  "tests/fileformats/jpeg/master/mandrill.jpg",
+  "tests/fileformats/jpeg/master/exif_overrun.jpg",
+  "tests/fileformats/jpeg/master/grayscale_test.jpg",
+  "tests/fileformats/jpeg/master/progressive.jpg",
+
+  "tests/fileformats/jpeg/master/testimg.jpg",
+  "tests/fileformats/jpeg/master/testimgp.jpg",
+  "tests/fileformats/jpeg/master/testorig.jpg",
+  "tests/fileformats/jpeg/master/testprog.jpg",
+]
+
+for file in files:
+  var img = decodeJpg(readFile(file))
+  # img.writeFile(file.replace("master", "generated").replace(".jpg", ".jpeg.png"))

tests/test_jpg.nim

@@ -1,6 +0,0 @@
-when defined(pixieUseStb):
-  import pixie/fileformats/jpg
-
-  let
-    original = readFile("tests/fileformats/jpg/jpeg420exif.jpg")
-    stbDecoded = decodeJpg(original)

tests/validate_jpeg.nim

@@ -1,3 +1,3 @@
 import pixie/fileformats/jpg, pixie/fileformats/stb_image/stb_image
 
-let original = readFile("tests/fileformats/jpg/jpeg420exif.jpg")
+let original = readFile("tests/fileformats/jpeg/jpeg420exif.jpg")