Pillow/PIL/PyAccess.py

#
# The Python Imaging Library
# Pillow fork
#
# Python implementation of the PixelAccess Object
#
# Copyright (c) 1997-2009 by Secret Labs AB.  All rights reserved.
# Copyright (c) 1995-2009 by Fredrik Lundh.
# Copyright (c) 2013 Eric Soroos
#
# See the README file for information on usage and redistribution
#

# Notes:
#
#  * Implements the pixel access object following Access.
#  * Does not implement the line functions, as they don't appear to be used
#  * Taking only the tuple form, which is used from python.
#    * Fill.c uses the integer form, but it's still going to use the old
#      Access.c implementation.
#

import logging
import sys

from cffi import FFI


logger = logging.getLogger(__name__)


defs = """
struct Pixel_RGBA {
    unsigned char r,g,b,a;
};
struct Pixel_I16 {
    unsigned char l,r;
};
"""
ffi = FFI()
ffi.cdef(defs)


class PyAccess(object):

    def __init__(self, img, readonly=False):
        vals = dict(img.im.unsafe_ptrs)
        self.readonly = readonly
        self.image8 = ffi.cast('unsigned char **', vals['image8'])
        self.image32 = ffi.cast('int **', vals['image32'])
        self.image = ffi.cast('unsigned char **', vals['image'])
        self.xsize, self.ysize = img.im.size

        # Keep pointer to im object to prevent dereferencing.
        self._im = img.im

        # Debugging is polluting test traces, only useful here
        # when hacking on PyAccess
        # logger.debug("%s", vals)
        self._post_init()

    def _post_init(self):
        pass

    def __setitem__(self, xy, color):
        """
        Modifies the pixel at x,y. The color is given as a single
        numerical value for single band images, and a tuple for
        multi-band images

        :param xy: The pixel coordinate, given as (x, y).
        :param value: The pixel value.
        """
        if self.readonly:
            raise ValueError('Attempt to putpixel a read only image')
        (x, y) = self.check_xy(xy)
        return self.set_pixel(x, y, color)

    def __getitem__(self, xy):
        """
        Returns the pixel at x,y. The pixel is returned as a single
        value for single band images or a tuple for multiple band
        images

        :param xy: The pixel coordinate, given as (x, y).
        :returns: a pixel value for single band images, a tuple of
          pixel values for multiband images.
        """

        (x, y) = self.check_xy(xy)
        return self.get_pixel(x, y)

    putpixel = __setitem__
    getpixel = __getitem__

    def check_xy(self, xy):
        (x, y) = xy
        if not (0 <= x < self.xsize and 0 <= y < self.ysize):
            raise ValueError('pixel location out of range')
        return xy


class _PyAccess32_2(PyAccess):
    """ PA, LA, stored in first and last bytes of a 32 bit word """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast("struct Pixel_RGBA **", self.image32)

    def get_pixel(self, x, y):
        pixel = self.pixels[y][x]
        return (pixel.r, pixel.a)

    def set_pixel(self, x, y, color):
        pixel = self.pixels[y][x]
        # tuple
        pixel.r = min(color[0], 255)
        pixel.a = min(color[1], 255)


class _PyAccess32_3(PyAccess):
    """ RGB and friends, stored in the first three bytes of a 32 bit word """

    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast("struct Pixel_RGBA **", self.image32)

    def get_pixel(self, x, y):
        pixel = self.pixels[y][x]
        return (pixel.r, pixel.g, pixel.b)

    def set_pixel(self, x, y, color):
        pixel = self.pixels[y][x]
        # tuple
        pixel.r = min(color[0], 255)
        pixel.g = min(color[1], 255)
        pixel.b = min(color[2], 255)
        pixel.a = 255


class _PyAccess32_4(PyAccess):
    """ RGBA etc, all 4 bytes of a 32 bit word """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast("struct Pixel_RGBA **", self.image32)

    def get_pixel(self, x, y):
        pixel = self.pixels[y][x]
        return (pixel.r, pixel.g, pixel.b, pixel.a)

    def set_pixel(self, x, y, color):
        pixel = self.pixels[y][x]
        # tuple
        pixel.r = min(color[0], 255)
        pixel.g = min(color[1], 255)
        pixel.b = min(color[2], 255)
        pixel.a = min(color[3], 255)


class _PyAccess8(PyAccess):
    """ 1, L, P, 8 bit images stored as uint8 """
    def _post_init(self, *args, **kwargs):
        self.pixels = self.image8

    def get_pixel(self, x, y):
        return self.pixels[y][x]

    def set_pixel(self, x, y, color):
        try:
            # integer
            self.pixels[y][x] = min(color, 255)
        except TypeError:
            # tuple
            self.pixels[y][x] = min(color[0], 255)


class _PyAccessI16_N(PyAccess):
    """ I;16 access, native bitendian without conversion """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast('unsigned short **', self.image)

    def get_pixel(self, x, y):
        return self.pixels[y][x]

    def set_pixel(self, x, y, color):
        try:
            # integer
            self.pixels[y][x] = min(color, 65535)
        except TypeError:
            # tuple
            self.pixels[y][x] = min(color[0], 65535)


class _PyAccessI16_L(PyAccess):
    """ I;16L access, with conversion """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast('struct Pixel_I16 **', self.image)

    def get_pixel(self, x, y):
        pixel = self.pixels[y][x]
        return pixel.l + pixel.r * 256

    def set_pixel(self, x, y, color):
        pixel = self.pixels[y][x]
        try:
            color = min(color, 65535)
        except TypeError:
            color = min(color[0], 65535)

        pixel.l = color & 0xFF
        pixel.r = color >> 8


class _PyAccessI16_B(PyAccess):
    """ I;16B access, with conversion """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast('struct Pixel_I16 **', self.image)

    def get_pixel(self, x, y):
        pixel = self.pixels[y][x]
        return pixel.l * 256 + pixel.r

    def set_pixel(self, x, y, color):
        pixel = self.pixels[y][x]
        try:
            color = min(color, 65535)
        except:
            color = min(color[0], 65535)

        pixel.l = color >> 8
        pixel.r = color & 0xFF


class _PyAccessI32_N(PyAccess):
    """ Signed Int32 access, native endian """
    def _post_init(self, *args, **kwargs):
        self.pixels = self.image32

    def get_pixel(self, x, y):
        return self.pixels[y][x]

    def set_pixel(self, x, y, color):
        self.pixels[y][x] = color


class _PyAccessI32_Swap(PyAccess):
    """ I;32L/B access, with byteswapping conversion """
    def _post_init(self, *args, **kwargs):
        self.pixels = self.image32

    def reverse(self, i):
        orig = ffi.new('int *', i)
        chars = ffi.cast('unsigned char *', orig)
        chars[0], chars[1], chars[2], chars[3] = chars[3], chars[2], \
            chars[1], chars[0]
        return ffi.cast('int *', chars)[0]

    def get_pixel(self, x, y):
        return self.reverse(self.pixels[y][x])

    def set_pixel(self, x, y, color):
        self.pixels[y][x] = self.reverse(color)


class _PyAccessF(PyAccess):
    """ 32 bit float access """
    def _post_init(self, *args, **kwargs):
        self.pixels = ffi.cast('float **', self.image32)

    def get_pixel(self, x, y):
        return self.pixels[y][x]

    def set_pixel(self, x, y, color):
        try:
            # not a tuple
            self.pixels[y][x] = color
        except TypeError:
            # tuple
            self.pixels[y][x] = color[0]


mode_map = {'1': _PyAccess8,
            'L': _PyAccess8,
            'P': _PyAccess8,
            'LA': _PyAccess32_2,
            'La': _PyAccess32_2,
            'PA': _PyAccess32_2,
            'RGB': _PyAccess32_3,
            'LAB': _PyAccess32_3,
            'HSV': _PyAccess32_3,
            'YCbCr': _PyAccess32_3,
            'RGBA': _PyAccess32_4,
            'RGBa': _PyAccess32_4,
            'RGBX': _PyAccess32_4,
            'CMYK': _PyAccess32_4,
            'F': _PyAccessF,
            'I': _PyAccessI32_N,
            }

if sys.byteorder == 'little':
    mode_map['I;16'] = _PyAccessI16_N
    mode_map['I;16L'] = _PyAccessI16_N
    mode_map['I;16B'] = _PyAccessI16_B

    mode_map['I;32L'] = _PyAccessI32_N
    mode_map['I;32B'] = _PyAccessI32_Swap
else:
    mode_map['I;16'] = _PyAccessI16_L
    mode_map['I;16L'] = _PyAccessI16_L
    mode_map['I;16B'] = _PyAccessI16_N

    mode_map['I;32L'] = _PyAccessI32_Swap
    mode_map['I;32B'] = _PyAccessI32_N


def new(img, readonly=False):
    access_type = mode_map.get(img.mode, None)
    if not access_type:
        logger.debug("PyAccess Not Implemented: %s", img.mode)
        return None
    return access_type(img, readonly)