Pillow/src/PIL/PpmImagePlugin.py

#
# The Python Imaging Library.
# $Id$
#
# PPM support for PIL
#
# History:
#       96-03-24 fl     Created
#       98-03-06 fl     Write RGBA images (as RGB, that is)
#
# Copyright (c) Secret Labs AB 1997-98.
# Copyright (c) Fredrik Lundh 1996.
#
# See the README file for information on usage and redistribution.
#
from __future__ import annotations

import math
from typing import IO

from . import Image, ImageFile
from ._binary import i16be as i16
from ._binary import o8
from ._binary import o32le as o32

#
# --------------------------------------------------------------------

b_whitespace = b"\x20\x09\x0a\x0b\x0c\x0d"

MODES = {
    # standard
    b"P1": "1",
    b"P2": "L",
    b"P3": "RGB",
    b"P4": "1",
    b"P5": "L",
    b"P6": "RGB",
    # extensions
    b"P0CMYK": "CMYK",
    b"Pf": "F",
    # PIL extensions (for test purposes only)
    b"PyP": "P",
    b"PyRGBA": "RGBA",
    b"PyCMYK": "CMYK",
}


def _accept(prefix: bytes) -> bool:
    return prefix[0:1] == b"P" and prefix[1] in b"0123456fy"


##
# Image plugin for PBM, PGM, and PPM images.


class PpmImageFile(ImageFile.ImageFile):
    format = "PPM"
    format_description = "Pbmplus image"

    def _read_magic(self) -> bytes:
        assert self.fp is not None

        magic = b""
        # read until whitespace or longest available magic number
        for _ in range(6):
            c = self.fp.read(1)
            if not c or c in b_whitespace:
                break
            magic += c
        return magic

    def _read_token(self) -> bytes:
        assert self.fp is not None

        token = b""
        while len(token) <= 10:  # read until next whitespace or limit of 10 characters
            c = self.fp.read(1)
            if not c:
                break
            elif c in b_whitespace:  # token ended
                if not token:
                    # skip whitespace at start
                    continue
                break
            elif c == b"#":
                # ignores rest of the line; stops at CR, LF or EOF
                while self.fp.read(1) not in b"\r\n":
                    pass
                continue
            token += c
        if not token:
            # Token was not even 1 byte
            msg = "Reached EOF while reading header"
            raise ValueError(msg)
        elif len(token) > 10:
            msg = f"Token too long in file header: {token.decode()}"
            raise ValueError(msg)
        return token

    def _open(self) -> None:
        assert self.fp is not None

        magic_number = self._read_magic()
        try:
            mode = MODES[magic_number]
        except KeyError:
            msg = "not a PPM file"
            raise SyntaxError(msg)
        self._mode = mode

        if magic_number in (b"P1", b"P4"):
            self.custom_mimetype = "image/x-portable-bitmap"
        elif magic_number in (b"P2", b"P5"):
            self.custom_mimetype = "image/x-portable-graymap"
        elif magic_number in (b"P3", b"P6"):
            self.custom_mimetype = "image/x-portable-pixmap"

        self._size = int(self._read_token()), int(self._read_token())

        decoder_name = "raw"
        if magic_number in (b"P1", b"P2", b"P3"):
            decoder_name = "ppm_plain"

        args: str | tuple[str | int, ...]
        if mode == "1":
            args = "1;I"
        elif mode == "F":
            scale = float(self._read_token())
            if scale == 0.0 or not math.isfinite(scale):
                msg = "scale must be finite and non-zero"
                raise ValueError(msg)
            self.info["scale"] = abs(scale)

            rawmode = "F;32F" if scale < 0 else "F;32BF"
            args = (rawmode, 0, -1)
        else:
            maxval = int(self._read_token())
            if not 0 < maxval < 65536:
                msg = "maxval must be greater than 0 and less than 65536"
                raise ValueError(msg)
            if maxval > 255 and mode == "L":
                self._mode = "I"

            rawmode = mode
            if decoder_name != "ppm_plain":
                # If maxval matches a bit depth, use the raw decoder directly
                if maxval == 65535 and mode == "L":
                    rawmode = "I;16B"
                elif maxval != 255:
                    decoder_name = "ppm"

            args = rawmode if decoder_name == "raw" else (rawmode, maxval)
        self.tile = [(decoder_name, (0, 0) + self.size, self.fp.tell(), args)]


#
# --------------------------------------------------------------------


class PpmPlainDecoder(ImageFile.PyDecoder):
    _pulls_fd = True
    _comment_spans: bool

    def _read_block(self) -> bytes:
        assert self.fd is not None

        return self.fd.read(ImageFile.SAFEBLOCK)

    def _find_comment_end(self, block: bytes, start: int = 0) -> int:
        a = block.find(b"\n", start)
        b = block.find(b"\r", start)
        return min(a, b) if a * b > 0 else max(a, b)  # lowest nonnegative index (or -1)

    def _ignore_comments(self, block: bytes) -> bytes:
        if self._comment_spans:
            # Finish current comment
            while block:
                comment_end = self._find_comment_end(block)
                if comment_end != -1:
                    # Comment ends in this block
                    # Delete tail of comment
                    block = block[comment_end + 1 :]
                    break
                else:
                    # Comment spans whole block
                    # So read the next block, looking for the end
                    block = self._read_block()

        # Search for any further comments
        self._comment_spans = False
        while True:
            comment_start = block.find(b"#")
            if comment_start == -1:
                # No comment found
                break
            comment_end = self._find_comment_end(block, comment_start)
            if comment_end != -1:
                # Comment ends in this block
                # Delete comment
                block = block[:comment_start] + block[comment_end + 1 :]
            else:
                # Comment continues to next block(s)
                block = block[:comment_start]
                self._comment_spans = True
                break
        return block

    def _decode_bitonal(self) -> bytearray:
        """
        This is a separate method because in the plain PBM format, all data tokens are
        exactly one byte, so the inter-token whitespace is optional.
        """
        data = bytearray()
        total_bytes = self.state.xsize * self.state.ysize

        while len(data) != total_bytes:
            block = self._read_block()  # read next block
            if not block:
                # eof
                break

            block = self._ignore_comments(block)

            tokens = b"".join(block.split())
            for token in tokens:
                if token not in (48, 49):
                    msg = b"Invalid token for this mode: %s" % bytes([token])
                    raise ValueError(msg)
            data = (data + tokens)[:total_bytes]
        invert = bytes.maketrans(b"01", b"\xFF\x00")
        return data.translate(invert)

    def _decode_blocks(self, maxval: int) -> bytearray:
        data = bytearray()
        max_len = 10
        out_byte_count = 4 if self.mode == "I" else 1
        out_max = 65535 if self.mode == "I" else 255
        bands = Image.getmodebands(self.mode)
        total_bytes = self.state.xsize * self.state.ysize * bands * out_byte_count

        half_token = b""
        while len(data) != total_bytes:
            block = self._read_block()  # read next block
            if not block:
                if half_token:
                    block = bytearray(b" ")  # flush half_token
                else:
                    # eof
                    break

            block = self._ignore_comments(block)

            if half_token:
                block = half_token + block  # stitch half_token to new block
                half_token = b""

            tokens = block.split()

            if block and not block[-1:].isspace():  # block might split token
                half_token = tokens.pop()  # save half token for later
                if len(half_token) > max_len:  # prevent buildup of half_token
                    msg = (
                        b"Token too long found in data: %s" % half_token[: max_len + 1]
                    )
                    raise ValueError(msg)

            for token in tokens:
                if len(token) > max_len:
                    msg = b"Token too long found in data: %s" % token[: max_len + 1]
                    raise ValueError(msg)
                value = int(token)
                if value < 0:
                    msg_str = f"Channel value is negative: {value}"
                    raise ValueError(msg_str)
                if value > maxval:
                    msg_str = f"Channel value too large for this mode: {value}"
                    raise ValueError(msg_str)
                value = round(value / maxval * out_max)
                data += o32(value) if self.mode == "I" else o8(value)
                if len(data) == total_bytes:  # finished!
                    break
        return data

    def decode(self, buffer: bytes) -> tuple[int, int]:
        self._comment_spans = False
        if self.mode == "1":
            data = self._decode_bitonal()
            rawmode = "1;8"
        else:
            maxval = self.args[-1]
            data = self._decode_blocks(maxval)
            rawmode = "I;32" if self.mode == "I" else self.mode
        self.set_as_raw(bytes(data), rawmode)
        return -1, 0


class PpmDecoder(ImageFile.PyDecoder):
    _pulls_fd = True

    def decode(self, buffer: bytes) -> tuple[int, int]:
        assert self.fd is not None

        data = bytearray()
        maxval = self.args[-1]
        in_byte_count = 1 if maxval < 256 else 2
        out_byte_count = 4 if self.mode == "I" else 1
        out_max = 65535 if self.mode == "I" else 255
        bands = Image.getmodebands(self.mode)
        dest_length = self.state.xsize * self.state.ysize * bands * out_byte_count
        while len(data) < dest_length:
            pixels = self.fd.read(in_byte_count * bands)
            if len(pixels) < in_byte_count * bands:
                # eof
                break
            for b in range(bands):
                value = (
                    pixels[b] if in_byte_count == 1 else i16(pixels, b * in_byte_count)
                )
                value = min(out_max, round(value / maxval * out_max))
                data += o32(value) if self.mode == "I" else o8(value)
        rawmode = "I;32" if self.mode == "I" else self.mode
        self.set_as_raw(bytes(data), rawmode)
        return -1, 0


#
# --------------------------------------------------------------------


def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
    if im.mode == "1":
        rawmode, head = "1;I", b"P4"
    elif im.mode == "L":
        rawmode, head = "L", b"P5"
    elif im.mode == "I":
        rawmode, head = "I;16B", b"P5"
    elif im.mode in ("RGB", "RGBA"):
        rawmode, head = "RGB", b"P6"
    elif im.mode == "F":
        rawmode, head = "F;32F", b"Pf"
    else:
        msg = f"cannot write mode {im.mode} as PPM"
        raise OSError(msg)
    fp.write(head + b"\n%d %d\n" % im.size)
    if head == b"P6":
        fp.write(b"255\n")
    elif head == b"P5":
        if rawmode == "L":
            fp.write(b"255\n")
        else:
            fp.write(b"65535\n")
    elif head == b"Pf":
        fp.write(b"-1.0\n")
    row_order = -1 if im.mode == "F" else 1
    ImageFile._save(
        im, fp, [ImageFile._Tile("raw", (0, 0) + im.size, 0, (rawmode, 0, row_order))]
    )


#
# --------------------------------------------------------------------


Image.register_open(PpmImageFile.format, PpmImageFile, _accept)
Image.register_save(PpmImageFile.format, _save)

Image.register_decoder("ppm", PpmDecoder)
Image.register_decoder("ppm_plain", PpmPlainDecoder)

Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm", ".pnm", ".pfm"])

Image.register_mime(PpmImageFile.format, "image/x-portable-anymap")