Merge pull request #363 from nnsee/ppm

Add PPM format support

README.md

@@ -37,6 +37,7 @@ BMP           | ✅           | ✅            |
 QOI           | ✅           | ✅            |
 GIF           | ✅           |               |
 SVG           | ✅           |               |
+PPM           | ✅           | ✅            |
 
 ### Font file formats
 

src/pixie.nim

@@ -1,13 +1,14 @@
 import bumpy, chroma, flatty/binny, os, pixie/common, pixie/contexts,
     pixie/fileformats/bmp, pixie/fileformats/gif, pixie/fileformats/jpg,
-    pixie/fileformats/png, pixie/fileformats/qoi, pixie/fileformats/svg,
-    pixie/fonts, pixie/images, pixie/masks, pixie/paints, pixie/paths, strutils, vmath
+    pixie/fileformats/png, pixie/fileformats/ppm, pixie/fileformats/qoi,
+    pixie/fileformats/svg, pixie/fonts, pixie/images, pixie/masks, pixie/paints,
+    pixie/paths, strutils, vmath
 
 export bumpy, chroma, common, contexts, fonts, images, masks, paints, paths, vmath
 
 type
   FileFormat* = enum
-    ffPng, ffBmp, ffJpg, ffGif, ffQoi
+    ffPng, ffBmp, ffJpg, ffGif, ffQoi, ffPpm
 
 converter autoStraightAlpha*(c: ColorRGBX): ColorRGBA {.inline, raises: [].} =
   ## Convert a premultiplied alpha RGBA to a straight alpha RGBA.
@@ -32,6 +33,8 @@ proc decodeImage*(data: string | seq[uint8]): Image {.raises: [PixieError].} =
     decodeGif(data)
   elif data.len > (14+8) and data.readStr(0, 4) == qoiSignature:
     decodeQoi(data)
+  elif data.len > 9 and data.readStr(0, 2) in ppmSignatures:
+    decodePpm(data)
   else:
     raise newException(PixieError, "Unsupported image file format")
 
@@ -69,6 +72,8 @@ proc encodeImage*(image: Image, fileFormat: FileFormat): string {.raises: [Pixie
     image.encodeQoi()
   of ffGif:
     raise newException(PixieError, "Unsupported file format")
+  of ffPpm:
+    image.encodePpm()
 
 proc encodeMask*(mask: Mask, fileFormat: FileFormat): string {.raises: [PixieError].} =
   ## Encodes a mask into memory.
@@ -85,6 +90,7 @@ proc writeFile*(image: Image, filePath: string) {.raises: [PixieError].} =
     of ".bmp": ffBmp
     of ".jpg", ".jpeg": ffJpg
     of ".qoi": ffQoi
+    of ".ppm": ffPpm
     else:
       raise newException(PixieError, "Unsupported file extension")
 
@@ -100,6 +106,7 @@ proc writeFile*(mask: Mask, filePath: string) {.raises: [PixieError].} =
     of ".bmp": ffBmp
     of ".jpg", ".jpeg": ffJpg
     of ".qoi": ffQoi
+    of ".ppm": ffPpm
     else:
       raise newException(PixieError, "Unsupported file extension")
 

src/pixie/fileformats/ppm.nim

@@ -0,0 +1,142 @@
+import chroma, flatty/binny, pixie/common, pixie/images, std/strutils
+
+# See: http://netpbm.sourceforge.net/doc/ppm.html
+
+const ppmSignatures* = @["P3", "P6"]
+
+type
+  PpmHeader = object
+    version: string
+    width, height, maxVal, dataOffset: int
+
+template failInvalid() =
+  raise newException(PixieError, "Invalid PPM data")
+
+proc decodeHeader(data: string): PpmHeader {.raises: [PixieError].} =
+  if data.len <= 10: # Each part + whitespace
+    raise newException(PixieError, "Invalid PPM file header")
+
+  var commentMode, readWhitespace: bool
+  var i, readFields: int
+  var field: string
+  while readFields < 4:
+    let c = readUint8(data, i).char
+    if c == '#':
+      commentMode = true
+    elif c == '\n':
+      commentMode = false
+    if not commentMode:
+      if c in Whitespace and not readWhitespace:
+        inc readFields
+        readWhitespace = true
+        try:
+          case readFields:
+            of 1:
+              result.version = field
+            of 2:
+              result.width = parseInt(field)
+            of 3:
+              result.height = parseInt(field)
+            of 4:
+              result.maxVal = parseInt(field)
+            else:
+              discard
+        except ValueError: failInvalid()
+        field = ""
+      elif not (c in Whitespace):
+        field.add(c)
+        readWhitespace = false
+    inc i
+
+    result.dataOffset = i
+
+proc decodeP6Data(data: string, maxVal: int): seq[ColorRGBX] {.raises: [].} =
+  let needsUint16 = maxVal > 0xFF
+
+  result = newSeq[ColorRGBX](
+    if needsUint16: data.len div 6
+    else: data.len div 3
+  )
+
+  # Let's calculate the real maximum value multiplier.
+  # rgbx() accepts a maximum value of 0xFF. Most of the time,
+  # maxVal is set to 0xFF as well, so in most cases it is 1
+  let valueMultiplier = 0xFF / maxVal
+
+  # if comparison in for loops is expensive, so let's unroll it
+  if not needsUint16:
+    for i in 0 ..< result.len:
+      let
+        red = (readUint8(data, i + (i * 2)).float * valueMultiplier + 0.5).uint8
+        green = (readUint8(data, i + 1 + (i * 2)).float * valueMultiplier + 0.5).uint8
+        blue = (readUint8(data, i + 2 + (i * 2)).float * valueMultiplier + 0.5).uint8
+      result[i] = rgbx(red, green, blue, 0xFF)
+  else:
+    for i in 0 ..< result.len:
+      let
+        red = (readUint16(data, i + (i * 5)).swap.float * valueMultiplier + 0.5).uint8
+        green = (readUint16(data, i + 2 + (i * 5)).swap.float * valueMultiplier + 0.5).uint8
+        blue = (readUint16(data, i + 4 + (i * 5)).swap.float * valueMultiplier + 0.5).uint8
+      result[i] = rgbx(red, green, blue, 0xFF)
+
+proc decodeP3Data(data: string, maxVal: int): seq[ColorRGBX] {.raises: [PixieError].} =
+  let needsUint16 = maxVal > 0xFF
+  let maxLen = (
+    if needsUint16: data.splitWhitespace.len * 2
+    else: data.splitWhitespace.len
+  )
+  var p6data = newStringOfCap(maxLen)
+
+  try:
+    if not needsUint16:
+      for line in data.splitLines():
+        for sample in line.split('#', 1)[0].splitWhitespace():
+          p6data.add(parseInt(sample).chr)
+    else:
+      for line in data.splitLines():
+        for sample in line.split('#', 1)[0].splitWhitespace():
+          p6data.addUint16(parseInt(sample).uint16.swap)
+  except ValueError: failInvalid()
+
+  result = decodeP6Data(p6data, maxVal)
+
+proc decodePpm*(data: string): Image {.raises: [PixieError].} =
+  ## Decodes Portable Pixel Map data into an Image.
+
+  let header = decodeHeader(data)
+
+  if not (header.version in ppmSignatures): failInvalid()
+  if 0 > header.maxVal or header.maxVal > 0xFFFF: failInvalid()
+
+  result = newImage(header.width, header.height)
+  result.data = (
+    if header.version == "P3":
+      decodeP3Data(data[header.dataOffset .. ^1], header.maxVal)
+    else: decodeP6Data(data[header.dataOffset .. ^1], header.maxVal)
+  )
+
+proc decodePpm*(data: seq[uint8]): Image {.inline, raises: [PixieError].} =
+  ## Decodes Portable Pixel Map data into an Image.
+  decodePpm(cast[string](data))
+
+proc encodePpm*(image: Image): string {.raises: [].} =
+  ## Encodes an image into the PPM file format (version P6).
+
+  # PPM header
+  result.add("P6") # The header field used to identify the PPM
+  result.add("\n") # Newline
+  result.add($image.width)
+  result.add(" ") # Space
+  result.add($image.height)
+  result.add("\n") # Newline
+  result.add("255") # Max color value
+  result.add("\n") # Newline
+
+  # PPM image data
+  for y in 0 ..< image.height:
+    for x in 0 ..< image.width:
+      let rgb = image[x, y]
+      # Alpha channel is ignored
+      result.addUint8(rgb.r)
+      result.addUint8(rgb.g)
+      result.addUint8(rgb.b)

tests/all.nim

@@ -10,6 +10,7 @@ import
   test_paints,
   test_paths,
   test_png,
+  test_ppm,
   test_qoi,
   test_svg,
   ../examples/text,

tests/fileformats/ppm/feep.p3.hidepth.master.ppm

@@ -0,0 +1,8 @@
+P3
+# feep.p3.hidepth.master.ppm
+4 4
+7919 # prime number chosen for test purposes
+ 0   0  0    0  0    0    0  0    0    7919 0 7919
+ 0   0  0    0 7919 3695  0  0    0     0   0  0
+ 0   0  0    0  0    0    0 7919 3695   0   0  0
+7919 0 7919  0  0    0    0  0    0     0   0  0

tests/fileformats/ppm/feep.p3.master.ppm

@@ -0,0 +1,8 @@
+P3
+# feep.p3.master.ppm
+4 4
+15
+ 0  0  0    0  0  0    0  0  0   15  0 15
+ 0  0  0    0 15  7    0  0  0    0  0  0
+ 0  0  0    0  0  0    0 15  7    0  0  0
+15  0 15    0  0  0    0  0  0    0  0  0

tests/test_ppm.nim

@@ -0,0 +1,18 @@
+import pixie/fileformats/ppm
+
+block:
+  for format in @["p3", "p6"]:
+    let image = decodePpm(readFile(
+      "tests/fileformats/ppm/feep." & $format & ".master.ppm"
+    ))
+    writeFile("tests/fileformats/ppm/feep." & $format & ".ppm", encodePpm(image))
+
+  let image = decodePpm(readFile(
+    "tests/fileformats/ppm/feep.p3.hidepth.master.ppm"
+  ))
+  writeFile("tests/fileformats/ppm/feep.p3.hidepth.ppm", encodePpm(image))
+
+  # produced output should be identical to P6 master
+  let p6Master = readFile("tests/fileformats/ppm/feep.p6.master.ppm")
+  for image in @["p3", "p6", "p3.hidepth"]:
+    doAssert readFile("tests/fileformats/ppm/feep." & $image & ".ppm") == p6Master