Merge pull request #575 from treeform/add-image-base64

Add image base64 helpers

Author: treeform

bindings/bindings.nim

@@ -112,6 +112,7 @@ exportRefObject Image:
     newImage(int, int)
   procs:
     writeFile(Image, string)
+    encodeBase64
     copy(Image)
     getColor
     setColor
@@ -291,6 +292,7 @@ exportRefObject Context:
     isPointInStroke(Context, Path, float32, float32)
 
 exportProcs:
+  decodeBase64
   decodeImage
   decodeImageDimensions
   readImage

src/pixie.nim

@@ -1,10 +1,11 @@
-import bumpy, chroma, flatty/binny, os, pixie/common, pixie/contexts,
-    pixie/fileformats/bmp, pixie/fileformats/gif, pixie/fileformats/jpeg,
-    pixie/fileformats/png, pixie/fileformats/ppm, pixie/fileformats/qoi,
-    pixie/fileformats/svg, pixie/fonts, pixie/images, pixie/internal,
-    pixie/paints, pixie/paths, strutils, vmath
+import
+  std/[os, strutils],
+  bumpy, chroma, flatty/binny, vmath,
+  pixie/[common, contexts, fonts, imagebase64, images, internal, paints, paths],
+  pixie/fileformats/[bmp, gif, jpeg, png, ppm, qoi, svg]
 
-export bumpy, chroma, common, contexts, fonts, images, paints, paths, vmath
+export bumpy, chroma, common, contexts, fonts, imagebase64, images, paints,
+    paths, vmath
 
 type
   FileFormat* = enum
@@ -85,7 +86,9 @@ proc readImage*(filePath: string): Image {.inline, raises: [PixieError].} =
   except IOError as e:
     raise newException(PixieError, e.msg, e)
 
-proc encodeImage*(image: Image, fileFormat: FileFormat): string {.raises: [PixieError].} =
+proc encodeImage*(
+  image: Image, fileFormat: FileFormat
+): string {.raises: [PixieError].} =
   ## Encodes an image into memory.
   case fileFormat:
   of PngFormat:

src/pixie/imagebase64.nim

@@ -0,0 +1,52 @@
+import
+  std/base64 as stdbase64,
+  std/strutils,
+  flatty/binny,
+  common,
+  fileformats/[bmp, gif, jpeg, png, ppm, qoi, svg]
+
+proc decodeImageData(data: string): Image {.raises: [PixieError].} =
+  ## Decodes supported image bytes into an image.
+  if data.len > 8 and data.readUint64(0) == cast[uint64](pngSignature):
+    decodePng(data).convertToImage()
+  elif data.len > 2 and data.readUint16(0) == cast[uint16](jpegStartOfImage):
+    decodeJpeg(data)
+  elif data.len > 2 and data.readStr(0, 2) == bmpSignature:
+    decodeBmp(data)
+  elif data.len > 5 and (
+    data.readStr(0, 5) == xmlSignature or
+    data.readStr(0, 4) == svgSignature
+  ):
+    newImage(parseSvg(data))
+  elif data.len > 6 and data.readStr(0, 6) in gifSignatures:
+    newImage(decodeGif(data))
+  elif data.len > (14 + 8) and data.readStr(0, 4) == qoiSignature:
+    decodeQoi(data).convertToImage()
+  elif data.len > 9 and data.readStr(0, 2) in ppmSignatures:
+    decodePpm(data)
+  else:
+    raise newException(PixieError, "Unsupported image file format")
+
+proc getPayload(data: string): string {.raises: [PixieError].} =
+  ## Gets the base64 payload from plain base64 data or a data URL.
+  if data.startsWith("data:"):
+    let comma = data.find(',')
+    if comma == -1:
+      raise newException(PixieError, "Invalid data URL")
+    if comma + 1 < data.len:
+      data[comma + 1 .. ^1]
+    else:
+      ""
+  else:
+    data
+
+proc encodeBase64*(image: Image): string {.raises: [PixieError].} =
+  ## Encodes an image into PNG format and returns it as base64.
+  stdbase64.encode(image.encodePng())
+
+proc decodeBase64*(data: string): Image {.raises: [PixieError].} =
+  ## Decodes a base64 image string into an image.
+  try:
+    decodeImageData(stdbase64.decode(data.getPayload()))
+  except ValueError as e:
+    raise newException(PixieError, e.msg, e)

tests/test_base64.nim

@@ -0,0 +1,35 @@
+import
+  std/base64,
+  chroma, pixie, pixie/fileformats/png
+
+block:
+  let image = newImage(2, 1)
+  image[0, 0] = rgba(255, 0, 0, 255)
+  image[1, 0] = rgba(0, 0, 255, 128)
+
+  let encoded = image.encodeBase64()
+  doAssert encoded == base64.encode(image.encodePng())
+
+  let decoded = decodeBase64(encoded)
+  doAssert decoded.width == image.width
+  doAssert decoded.height == image.height
+  doAssert decoded.data == image.data
+
+block:
+  let image = newImage(1, 1)
+  image[0, 0] = rgba(0, 255, 0, 255)
+
+  let
+    encoded = image.encodeBase64()
+    decoded = decodeBase64("data:image/png;base64," & encoded)
+
+  doAssert decoded.width == image.width
+  doAssert decoded.height == image.height
+  doAssert decoded.data == image.data
+
+block:
+  try:
+    discard decodeBase64("nope")
+    doAssert false
+  except PixieError:
+    discard

tests/tests.nim

@@ -1,4 +1,5 @@
 import
+  test_base64,
   test_bmp,
   test_contexts,
   test_fonts,