decodeImageDimensions(data) and readImageDimensions(path)

bindings/bindings.nim

@@ -93,6 +93,9 @@ exportObject ColorStop:
 exportObject TextMetrics:
   discard
 
+exportObject ImageDimensions:
+  discard
+
 exportSeq seq[float32]:
   discard
 
@@ -310,7 +313,10 @@ exportRefObject Context:
     isPointInStroke(Context, Path, float32, float32)
 
 exportProcs:
+  decodeImage
+  decodeImageDimensions
   readImage
+  readImageDimensions
   readmask
   readTypeface
   readFont

src/pixie.nim

@@ -18,6 +18,25 @@ converter autoPremultipliedAlpha*(c: ColorRGBA): ColorRGBX {.inline, raises: [].
   ## Convert a straight alpha RGBA to a premultiplied alpha RGBA.
   c.rgbx()
 
+proc decodeImageDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes an image's dimensions from memory.
+  if data.len > 8 and data.readUint64(0) == cast[uint64](pngSignature):
+    decodePngDimensions(data)
+  elif data.len > 2 and data.readUint16(0) == cast[uint16](jpegStartOfImage):
+    decodeJpegDimensions(data)
+  elif data.len > 2 and data.readStr(0, 2) == bmpSignature:
+    decodeBmpDimensions(data)
+  elif data.len > 6 and data.readStr(0, 6) in gifSignatures:
+    decodeGifDimensions(data)
+  elif data.len > (14+8) and data.readStr(0, 4) == qoiSignature:
+    decodeQoiDimensions(data)
+  elif data.len > 9 and data.readStr(0, 2) in ppmSignatures:
+    decodePpmDimensions(data)
+  else:
+    raise newException(PixieError, "Unsupported image file format")
+
 proc decodeImage*(data: string): Image {.raises: [PixieError].} =
   ## Loads an image from memory.
   if data.len > 8 and data.readUint64(0) == cast[uint64](pngSignature):
@@ -45,6 +64,15 @@ proc decodeMask*(data: string): Mask {.raises: [PixieError].} =
   else:
     raise newException(PixieError, "Unsupported mask file format")
 
+proc readImageDimensions*(
+  filePath: string
+): ImageDimensions {.inline, raises: [PixieError].} =
+  ## Loads an image from a file.
+  try:
+    decodeImageDimensions(readFile(filePath))
+  except IOError as e:
+    raise newException(PixieError, e.msg, e)
+
 proc readImage*(filePath: string): Image {.inline, raises: [PixieError].} =
   ## Loads an image from a file.
   try:

src/pixie/common.nim

@@ -28,6 +28,9 @@ type
     SubtractMaskBlend ## Inverse mask
     ExcludeMaskBlend
 
+  ImageDimensions* = object
+    width*, height*: int
+
 proc mix*(a, b: uint8, t: float32): uint8 {.inline, raises: [].} =
   ## Linearly interpolate between a and b using t.
   let t = round(t * 255).uint32

src/pixie/fileformats/bmp.nim

@@ -227,6 +227,21 @@ proc decodeBmp*(data: string): Image {.raises: [PixieError].} =
 
   decodeDib(data[14].unsafeAddr, data.len - 14)
 
+proc decodeBmpDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the BMP dimensions.
+
+  if data.len < 26:
+    failInvalid()
+
+  # BMP Header
+  if data[0 .. 1] != "BM":
+    failInvalid()
+
+  result.width = data.readInt32(18).int
+  result.height = abs(data.readInt32(22)).int
+
 proc encodeBmp*(image: Image): string {.raises: [].} =
   ## Encodes an image into the BMP file format.
 

src/pixie/fileformats/gif.nim

@@ -178,5 +178,18 @@ proc decodeGif*(data: string): Image {.raises: [PixieError].} =
     else:
       raise newException(PixieError, "Invalid GIF block type")
 
+proc decodeGifDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the GIF dimensions.
+  if data.len < 10:
+    failInvalid()
+
+  if data[0 .. 5] notin gifSignatures:
+    raise newException(PixieError, "Invalid GIF file signature")
+
+  result.width = data.readInt16(6).int
+  result.height = data.readInt16(8).int
+
 when defined(release):
   {.pop.}

src/pixie/fileformats/jpeg.nim

@@ -1056,7 +1056,7 @@ proc decodeJpeg*(data: string): Image {.raises: [PixieError].} =
         state.decodeDHT()
       of 0xD8:
         # SOI - Start of Image
-        continue
+        discard
       of 0xD9:
         # EOI - End of Image
         break
@@ -1094,5 +1094,63 @@ proc decodeJpeg*(data: string): Image {.raises: [PixieError].} =
 
   state.buildImage()
 
+proc decodeJpegDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the JPEG dimensions.
+
+  var state = DecoderState()
+  state.buffer = cast[ptr UncheckedArray[uint8]](data.cstring)
+  state.len = data.len
+
+  while true:
+    if state.readUint8() != 0xFF:
+      failInvalid("invalid chunk marker")
+
+    let chunkId = state.readUint8()
+    case chunkId:
+      of 0xD8:
+        # SOI - Start of Image
+        discard
+      of 0xC0:
+        # Start Of Frame (Baseline DCT)
+        state.decodeSOF0()
+        break
+      of 0xC1:
+        # Start Of Frame (Extended sequential DCT)
+        state.decodeSOF1()
+        break
+      of 0xC2:
+        # Start Of Frame (Progressive DCT)
+        state.decodeSOF2()
+        break
+      of 0xDB:
+        # Define Quantization Table(s)
+        state.skipChunk()
+      of 0XE0:
+        # Application-specific
+        state.skipChunk()
+      of 0xE1:
+        # Exif/APP1
+        state.decodeExif()
+      of 0xE2..0xEF:
+        # Application-specific
+        state.skipChunk()
+      of 0xFE:
+        # Comment
+        state.skipChunk()
+      else:
+        failInvalid("invalid chunk " & chunkId.toHex())
+
+  case state.orientation:
+    of 0, 1, 2, 3, 4:
+      result.width = state.imageWidth
+      result.height = state.imageHeight
+    of 5, 6, 7, 8:
+      result.width = state.imageHeight
+      result.height = state.imageWidth
+    else:
+      failInvalid("invalid orientation")
+
 when defined(release):
   {.pop.}

src/pixie/fileformats/png.nim

@@ -341,6 +341,26 @@ proc newImage*(png: Png): Image {.raises: [PixieError].} =
   copyMem(result.data[0].addr, png.data[0].addr, png.data.len * 4)
   result.data.toPremultipliedAlpha()
 
+proc decodePngDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the PNG dimensions.
+  if data.len < (8 + (8 + 13 + 4) + 4): # Magic bytes + IHDR + IEND
+    failInvalid()
+
+  # PNG file signature
+  let signature = cast[array[8, uint8]](data.readUint64(0))
+  if signature != pngSignature:
+    failInvalid()
+
+  # First chunk must be IHDR
+  if data.readUint32(8).swap() != 13 or data.readStr(12, 4) != "IHDR":
+    failInvalid()
+
+  let header = decodeHeader(data[16 ..< 16 + 13])
+  result.width = header.width
+  result.height = header.height
+
 proc decodePng*(data: string): Png {.raises: [PixieError].} =
   ## Decodes the PNG data.
   if data.len < (8 + (8 + 13 + 4) + 4): # Magic bytes + IHDR + IEND

src/pixie/fileformats/ppm.nim

@@ -135,6 +135,14 @@ proc decodePpm*(data: string): Image {.raises: [PixieError].} =
     else:
       decodeP6Data(data[header.dataOffset .. ^1], header.maxVal)
 
+proc decodePpmDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the PPM dimensions.
+  let header = decodeHeader(data)
+  result.width = header.width
+  result.height = header.height
+
 proc encodePpm*(image: Image): string {.raises: [].} =
   ## Encodes an image into the PPM file format (version P6).
 

src/pixie/fileformats/qoi.nim

@@ -121,6 +121,16 @@ proc decodeQoi*(data: string): Qoi {.raises: [PixieError].} =
       raise newException(PixieError, "Invalid QOI padding")
     inc(p)
 
+proc decodeQoiDimensions*(
+  data: string
+): ImageDimensions {.raises: [PixieError].} =
+  ## Decodes the QOI dimensions.
+  if data.len <= 12 or data[0 .. 3] != qoiSignature:
+    raise newException(PixieError, "Invalid QOI header")
+
+  result.width = data.readUint32(4).swap().int
+  result.height = data.readUint32(8).swap().int
+
 proc encodeQoi*(qoi: Qoi): string {.raises: [PixieError].} =
   ## Encodes raw QOI pixels to the QOI file format.
 

tests/test_bmp.nim

@@ -1,4 +1,4 @@
-import chroma, os, pixie, pixie/fileformats/bmp, strutils
+import os, pixie/fileformats/bmp
 
 # block:
 #   var image = newImage(4, 2)
@@ -32,9 +32,9 @@ import chroma, os, pixie, pixie/fileformats/bmp, strutils
 
 block:
   for bits in [32, 24]:
-    let image = decodeBmp(readFile(
-      "tests/fileformats/bmp/knight." & $bits & ".master.bmp"
-    ))
+    let
+      path = "tests/fileformats/bmp/knight." & $bits & ".master.bmp"
+      image = decodeBmp(readFile(path))
     writeFile("tests/fileformats/bmp/knight." & $bits & ".bmp", encodeBmp(image))
 
 block:
@@ -46,5 +46,9 @@ block:
 block:
   for file in walkFiles("tests/fileformats/bmp/bmpsuite/*"):
     # echo file
-    let image = decodeBmp(readFile(file))
+    let
+      image = decodeBmp(readFile(file))
+      dimensions = decodeBmpDimensions(readFile(file))
     #image.writeFile(file.replace("bmpsuite", "output") & ".png")
+    doAssert image.width == dimensions.width
+    doAssert image.height == dimensions.height

tests/test_gif.nim

@@ -1,13 +1,37 @@
 import pixie, pixie/fileformats/gif
 
-var img = decodeGIF(readFile("tests/fileformats/gif/3x5.gif"))
-img.writeFile("tests/fileformats/gif/3x5.png")
+block:
+  let
+    path = "tests/fileformats/gif/3x5.gif"
+    image = decodeGIF(readFile(path))
+    dimensions = decodeGifDimensions(readFile(path))
+  image.writeFile("tests/fileformats/gif/3x5.png")
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height
 
-var img2 = decodeGIF(readFile("tests/fileformats/gif/audrey.gif"))
-img2.writeFile("tests/fileformats/gif/audrey.png")
+block:
+  let
+    path = "tests/fileformats/gif/audrey.gif"
+    image = decodeGIF(readFile(path))
+    dimensions = decodeGifDimensions(readFile(path))
+  image.writeFile("tests/fileformats/gif/audrey.png")
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height
 
-var img3 = decodeGIF(readFile("tests/fileformats/gif/sunflower.gif"))
-img3.writeFile("tests/fileformats/gif/sunflower.png")
+block:
+  let
+    path = "tests/fileformats/gif/sunflower.gif"
+    image = decodeGIF(readFile(path))
+    dimensions = decodeGifDimensions(readFile(path))
+  image.writeFile("tests/fileformats/gif/sunflower.png")
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height
 
-var img4 = readImage("tests/fileformats/gif/sunflower.gif")
-doAssert img3.data == img4.data
+block:
+  let
+    path = "tests/fileformats/gif/sunflower.gif"
+    image = decodeGIF(readFile(path))
+    dimensions = decodeGifDimensions(readFile(path))
+  image.writeFile("tests/fileformats/gif/sunflower.png")
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height

tests/test_jpeg.nim

@@ -1,4 +1,8 @@
-import jpegsuite, pixie
+import jpegsuite, pixie, pixie/fileformats/jpeg
 
 for file in jpegSuiteFiles:
-  let img = readImage(file)
+  let
+    image = readImage(file)
+    dimensions = decodeJpegDimensions(readFile(file))
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height

tests/test_png.nim

@@ -33,3 +33,9 @@ block:
 
 block:
   discard readImage("tests/fileformats/png/trailing_data.png")
+
+block:
+  let dimensions =
+    decodeImageDimensions(readFile("tests/fileformats/png/mandrill.png"))
+  doAssert dimensions.width == 512
+  doAssert dimensions.height == 512

tests/test_ppm.nim

@@ -2,13 +2,22 @@ import pixie/fileformats/ppm
 
 block:
   for format in @["p3", "p6"]:
-    let image = decodePpm(readFile(
-      "tests/fileformats/ppm/feep." & $format & ".master.ppm"
-    ))
+    let
+      path = "tests/fileformats/ppm/feep." & $format & ".master.ppm"
+      image = decodePpm(readFile(path))
+      dimensions = decodePpmDimensions(readFile(path))
     writeFile("tests/fileformats/ppm/feep." & $format & ".ppm", encodePpm(image))
+    doAssert image.width == dimensions.width
+    doAssert image.height == dimensions.height
 
-  let image = decodePpm(readFile("tests/fileformats/ppm/feep.p3.hidepth.master.ppm"))
+block:
+  let
+    path = "tests/fileformats/ppm/feep.p3.hidepth.master.ppm"
+    image = decodePpm(readFile(path))
+    dimensions = decodePpmDimensions(readFile(path))
   writeFile("tests/fileformats/ppm/feep.p3.hidepth.ppm", encodePpm(image))
+  doAssert image.width == dimensions.width
+  doAssert image.height == dimensions.height
 
   # produced output should be identical to P6 master
   let p6Master = readFile("tests/fileformats/ppm/feep.p6.master.ppm")

tests/test_qoi.nim

@@ -4,14 +4,19 @@ const tests = ["testcard", "testcard_rgba"]
 
 for name in tests:
   let
-    input = readImage("tests/fileformats/qoi/" & name & ".qoi")
+    path = "tests/fileformats/qoi/" & name & ".qoi"
+    input = readImage(path)
     control = readImage("tests/fileformats/qoi/" & name & ".png")
+    dimensions = decodeQoiDimensions(readFile(path))
   doAssert input.data == control.data, "input mismatch of " & name
+  doAssert input.width == dimensions.width
+  doAssert input.height == dimensions.height
   discard encodeQoi(control)
 
 for name in tests:
   let
-    input = decodeQoi(readFile("tests/fileformats/qoi/" & name & ".qoi"))
+    path = "tests/fileformats/qoi/" & name & ".qoi"
+    input = decodeQoi(readFile(path))
     output = decodeQoi(encodeQoi(input))
   doAssert output.data.len == input.data.len
   doAssert output.data == input.data