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Added transparency support for GIFs, palette-based PNGs and grayscale PNGs

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Tamás Zahola 2021-06-19 01:08:18 +02:00
parent 87d524bab0
commit 06b4a4902a
1 changed files with 76 additions and 48 deletions
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124
src/img2pdf.py
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@ -85,9 +85,9 @@ FitMode = Enum("FitMode", "into fill exact shrink enlarge")
PageOrientation = Enum("PageOrientation", "portrait landscape") PageOrientation = Enum("PageOrientation", "portrait landscape")
Colorspace = Enum("Colorspace", "RGB L 1 CMYK CMYK;I RGBA P other") Colorspace = Enum("Colorspace", "RGB RGBA L LA 1 CMYK CMYK;I P other")
ImageFormat = Enum("ImageFormat", "JPEG JPEG2000 CCITTGroup4 PNG TIFF MPO other") ImageFormat = Enum("ImageFormat", "JPEG JPEG2000 CCITTGroup4 PNG GIF TIFF MPO other")
PageMode = Enum("PageMode", "none outlines thumbs") PageMode = Enum("PageMode", "none outlines thumbs")
@ -760,7 +760,7 @@ class pdfdoc(object):
artborder=None, artborder=None,
iccp=None, iccp=None,
): ):
assert color != Colorspace.RGBA or (imgformat == ImageFormat.PNG and smaskdata is not None) assert (color != Colorspace.RGBA and color != Colorspace.LA) or (imgformat == ImageFormat.PNG and smaskdata is not None)
if self.engine == Engine.pikepdf: if self.engine == Engine.pikepdf:
PdfArray = pikepdf.Array PdfArray = pikepdf.Array
@ -780,7 +780,7 @@ class pdfdoc(object):
TrueObject = True if self.engine == Engine.pikepdf else PdfObject("true") TrueObject = True if self.engine == Engine.pikepdf else PdfObject("true")
FalseObject = False if self.engine == Engine.pikepdf else PdfObject("false") FalseObject = False if self.engine == Engine.pikepdf else PdfObject("false")
if color == Colorspace["1"] or color == Colorspace.L: if color == Colorspace["1"] or color == Colorspace.L or color == Colorspace.LA:
colorspace = PdfName.DeviceGray colorspace = PdfName.DeviceGray
elif color == Colorspace.RGB or color == Colorspace.RGBA: elif color == Colorspace.RGB or color == Colorspace.RGBA:
colorspace = PdfName.DeviceRGB colorspace = PdfName.DeviceRGB
@ -819,7 +819,7 @@ class pdfdoc(object):
else: else:
iccpdict = PdfDict(stream=convert_load(iccp)) iccpdict = PdfDict(stream=convert_load(iccp))
iccpdict[PdfName.Alternate] = colorspace iccpdict[PdfName.Alternate] = colorspace
if color == Colorspace["1"] or color == Colorspace.L: if color == Colorspace["1"] or color == Colorspace.L or color == Colorspace.LA:
iccpdict[PdfName.N] = 1 iccpdict[PdfName.N] = 1
elif color == Colorspace.RGB or color == Colorspace.RGBA: elif color == Colorspace.RGB or color == Colorspace.RGBA:
iccpdict[PdfName.N] = 3 iccpdict[PdfName.N] = 3
@ -872,7 +872,7 @@ class pdfdoc(object):
decodeparms[PdfName.Rows] = imgheightpx decodeparms[PdfName.Rows] = imgheightpx
image[PdfName.DecodeParms] = [decodeparms] image[PdfName.DecodeParms] = [decodeparms]
elif imgformat is ImageFormat.PNG: elif imgformat is ImageFormat.PNG:
if color == Colorspace.RGBA: if smaskdata is not None:
if self.engine == Engine.pikepdf: if self.engine == Engine.pikepdf:
smask = self.writer.make_stream(smaskdata) smask = self.writer.make_stream(smaskdata)
else: else:
@ -890,16 +890,16 @@ class pdfdoc(object):
# /SMask requires PDF 1.4 # /SMask requires PDF 1.4
if self.output_version < "1.4": if self.output_version < "1.4":
self.output_version = "1.4" self.output_version = "1.4"
decodeparms = PdfDict()
decodeparms[PdfName.Predictor] = 15
if color in [Colorspace.P, Colorspace["1"], Colorspace.L, Colorspace.LA]:
decodeparms[PdfName.Colors] = 1
else: else:
decodeparms = PdfDict() decodeparms[PdfName.Colors] = 3
decodeparms[PdfName.Predictor] = 15 decodeparms[PdfName.Columns] = imgwidthpx
if color in [Colorspace.P, Colorspace["1"], Colorspace.L]: decodeparms[PdfName.BitsPerComponent] = depth
decodeparms[PdfName.Colors] = 1 image[PdfName.DecodeParms] = decodeparms
else:
decodeparms[PdfName.Colors] = 3
decodeparms[PdfName.Columns] = imgwidthpx
decodeparms[PdfName.BitsPerComponent] = depth
image[PdfName.DecodeParms] = decodeparms
text = ( text = (
"q\n%0.4f 0 0 %0.4f %0.4f %0.4f cm\n/Im0 Do\nQ" "q\n%0.4f 0 0 %0.4f %0.4f %0.4f cm\n/Im0 Do\nQ"
@ -1208,8 +1208,19 @@ def get_imgmetadata(
ndpi = (int(round(ndpi[0])), int(round(ndpi[1]))) ndpi = (int(round(ndpi[0])), int(round(ndpi[1])))
ics = imgdata.mode ics = imgdata.mode
if imgformat == ImageFormat.PNG and ics == "RGBA": # GIF and PNG files with transparency are supported
logger.warning("Image contains an alpha channel which will be stored as a separate soft mask (/SMask) image in PDF.") if (
(imgformat == ImageFormat.PNG or imgformat == ImageFormat.GIF)
and (ics in ["RGBA", "LA"] or "transparency" in imgdata.info)
):
# Must check the IHDR chunk for the bit depth, because PIL would lossily
# convert 16-bit RGBA/LA images to 8-bit.
if imgformat == ImageFormat.PNG and rawdata != None:
depth = rawdata[24]
if depth > 8:
logger.warning("Image with transparency and a bit depth of %d." % depth)
logger.warning("This is unsupported due to PIL limitations.")
raise AlphaChannelError("Refusing to work with multiple >8bit channels.")
elif (ics in ["LA", "PA", "RGBA"] or "transparency" in imgdata.info): elif (ics in ["LA", "PA", "RGBA"] or "transparency" in imgdata.info):
logger.warning("Image contains transparency which cannot be retained in PDF.") logger.warning("Image contains transparency which cannot be retained in PDF.")
logger.warning("img2pdf will not perform a lossy operation.") logger.warning("img2pdf will not perform a lossy operation.")
@ -1523,7 +1534,7 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
img_page_count += 1 img_page_count += 1
cleanup() cleanup()
return result return result
# We can directly embed the IDAT chunk of PNG images if the PNG is not # We can directly embed the IDAT chunk of PNG images if the PNG is not
# interlaced # interlaced
# #
@ -1531,21 +1542,12 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
# or not. Thus, we retrieve that info manually by looking at byte 13 in the # or not. Thus, we retrieve that info manually by looking at byte 13 in the
# IHDR chunk. We know where to find that in the file because the IHDR chunk # IHDR chunk. We know where to find that in the file because the IHDR chunk
# must be the first chunk. # must be the first chunk.
if imgformat == ImageFormat.PNG: if imgformat == ImageFormat.PNG and rawdata[28] == 0:
color, ndpi, imgwidthpx, imgheightpx, rotation, iccp = get_imgmetadata( color, ndpi, imgwidthpx, imgheightpx, rotation, iccp = get_imgmetadata(
imgdata, imgformat, default_dpi, colorspace, rawdata, rot imgdata, imgformat, default_dpi, colorspace, rawdata, rot
) )
if color != Colorspace.RGBA and color != Colorspace.LA and "transparency" not in imgdata.info:
if color == Colorspace.RGBA or rawdata[28] == 0: pngidat, palette = parse_png(rawdata)
if color == Colorspace.RGBA:
r, g, b, a = imgdata.split()
pngdata = zlib.compress(Image.merge("RGB", (r, g, b)).tobytes())
smaskdata = zlib.compress(a.tobytes())
palette = None
else:
pngdata, palette = parse_png(rawdata)
smaskdata = None
# PIL does not provide the information about the original bits per # PIL does not provide the information about the original bits per
# sample. Thus, we retrieve that info manually by looking at byte 9 in # sample. Thus, we retrieve that info manually by looking at byte 9 in
# the IHDR chunk. We know where to find that in the file because the # the IHDR chunk. We know where to find that in the file because the
@ -1560,8 +1562,8 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
color, color,
ndpi, ndpi,
imgformat, imgformat,
pngdata, pngidat,
smaskdata, None,
imgwidthpx, imgwidthpx,
imgheightpx, imgheightpx,
palette, palette,
@ -1703,7 +1705,9 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
color = Colorspace.L color = Colorspace.L
elif color in [ elif color in [
Colorspace.RGB, Colorspace.RGB,
Colorspace.RGBA,
Colorspace.L, Colorspace.L,
Colorspace.LA,
Colorspace.CMYK, Colorspace.CMYK,
Colorspace["CMYK;I"], Colorspace["CMYK;I"],
Colorspace.P, Colorspace.P,
@ -1734,28 +1738,35 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
) )
) )
else: else:
# cheapo version to retrieve a PNG encoding of the payload is to if color == Colorspace.RGBA or color == Colorspace.LA or "transparency" in newimg.info:
# just save it with PIL. In the future this could be replaced by if color == Colorspace.RGBA:
# dedicated function applying the Paeth PNG filter to the raw pixel newcolor = color
pngbuffer = BytesIO() r, g, b, a = newimg.split()
newimg.save(pngbuffer, format="png") newimg = Image.merge("RGB", (r, g, b))
pngidat, palette = parse_png(pngbuffer.getvalue()) elif color == Colorspace.LA:
# PIL does not provide the information about the original bits per newcolor = color
# sample. Thus, we retrieve that info manually by looking at byte 9 in l, a = newimg.split()
# the IHDR chunk. We know where to find that in the file because the newimg = l
# IHDR chunk must be the first chunk else:
pngbuffer.seek(24) newcolor = Colorspace.RGBA
depth = ord(pngbuffer.read(1)) r, g, b, a = newimg.convert(mode="RGBA").split()
if depth not in [1, 2, 4, 8, 16]: newimg = Image.merge("RGB", (r, g, b))
raise ValueError("invalid bit depth: %d" % depth)
smaskdata = zlib.compress(a.tobytes())
logger.warning("Image contains an alpha channel which will be stored as a separate soft mask (/SMask) image in PDF.")
else:
newcolor = color
smaskdata = None
pngidat, palette, depth = to_png_data(newimg)
logger.debug("read_images() encoded an image as PNG") logger.debug("read_images() encoded an image as PNG")
result.append( result.append(
( (
color, newcolor,
ndpi, ndpi,
ImageFormat.PNG, ImageFormat.PNG,
pngidat, pngidat,
None, smaskdata,
imgwidthpx, imgwidthpx,
imgheightpx, imgheightpx,
palette, palette,
@ -1769,6 +1780,23 @@ def read_images(rawdata, colorspace, first_frame_only=False, rot=None):
cleanup() cleanup()
return result return result
def to_png_data(img):
# cheapo version to retrieve a PNG encoding of the payload is to
# just save it with PIL. In the future this could be replaced by
# dedicated function applying the Paeth PNG filter to the raw pixel
pngbuffer = BytesIO()
img.save(pngbuffer, format="png")
pngidat, palette = parse_png(pngbuffer.getvalue())
# PIL does not provide the information about the original bits per
# sample. Thus, we retrieve that info manually by looking at byte 9 in
# the IHDR chunk. We know where to find that in the file because the
# IHDR chunk must be the first chunk
pngbuffer.seek(24)
depth = ord(pngbuffer.read(1))
if depth not in [1, 2, 4, 8, 16]:
raise ValueError("invalid bit depth: %d" % depth)
return pngidat, palette, depth
# converts a length in pixels to a length in PDF units (1/72 of an inch) # converts a length in pixels to a length in PDF units (1/72 of an inch)
def px_to_pt(length, dpi): def px_to_pt(length, dpi):