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+"""
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+Image non-geospatial operations and manipulations
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+
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+Note: Functions in this module are experimental and are not considered
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+a stable API, i.e. may change in future releases of GRASS GIS.
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+
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+It heavily relies on PIL but unlike PIL, the functions operate on
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+files instead of PIL Image objects (which are used internally).
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+These functions are convenient for post-processing outputs from GRASS
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+modules, e.g. after rendering. However, if you have multiple operations
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+you may want to consider using PIL directly for efficiency (to avoid
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+writing and reading from the files).
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+
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+Usage
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+=====
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+
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+Use keyword arguments for all parameters other than those for input,
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+output, and format. All function provide reasonable defaults if possible,
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+but note that they may not be applicable to you case or when developing
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+a general tool.
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+
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+>>> import grass.imaging.operations as iop
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+
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+>>> # replace white color in the image by 100% transparency
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+>>> iop.change_rbg_to_transparent("map.png", color=(255, 255, 255))
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+
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+>>> # crop the image in place
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+>>> iop.crop_image("map.png")
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+
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+>>> # create a new image with inverted colors of the original image
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+>>> iop.invert_image_colors("map.png", "map_inverted.png")
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+
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+>>> # create a thumbnail of the original image
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+>>> iop.thumbnail_image("map.png", "map_thumbnail.png", size=(64, 64))
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+
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+Error handling
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+==============
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+
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+When PIL or a required submodule is not available, a RuntimeError
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+exception is raised with a message mentioning the missing dependency.
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+Additionally, any of the exceptions raised by PIL may be raised too,
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+for example, when the file is not found.
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+
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+Authors, copyright and license
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+==============================
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+
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+(C) 2018 by Vaclav Petras and the GRASS Development Team
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+
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+This program is free software under the GNU General Public
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+License (>=v2). Read the file COPYING that comes with GRASS
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+for details.
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+
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+.. sectionauthor:: Vaclav Petras <wenzeslaus gmail com>
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+"""
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+
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+
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+# import similar to what is in visvis
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+try:
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+ import PIL
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+ from PIL import Image
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+ PILLOW = True
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+ try:
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+ from PIL import PILLOW_VERSION # pylint: disable=unused-import
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+ except ImportError:
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+ PILLOW = False
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+ try:
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+ import PIL.ImageOps as ImageOps
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+ except ImportError:
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+ ImageOps = None
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+except ImportError:
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+ PIL = None
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+
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+
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+def crop_image(input_file, output_file=None, format=None):
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+ """Crop to non-zero area of the image
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+
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+ :param input_file: Name of the file to manipulate
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+ :param output_file: filename for the new file (same as input by default)
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+ :param format: format to be used new file (if different from extension)
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+ """
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+ if PIL is None:
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+ raise RuntimeError(_("Install PIL or Pillow to use this function"))
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+ if not output_file:
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+ output_file = input_file
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+ img = Image.open(input_file)
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+ box = img.getbbox()
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+ cropped_image = img.crop(box)
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+ cropped_image.save(output_file, format)
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+
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+
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+def thumbnail_image(input_file, output_file=None, size=(200, 200),
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+ format=None):
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+ """Create a thumbnail of an image
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+
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+ The image aspect ratio is kept and its height and width are adjusted
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+ accordingly to fit the ``size`` parameter.
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+
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+ :param input_file: Name of the file to manipulate
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+ :param size: Size of the new image in pixels as tuple
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+ :param output_file: filename for the new file (same as input by default)
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+ :param format: format to be used new file (if different from extension)
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+ """
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+ if PIL is None:
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+ raise RuntimeError(_("Install PIL or Pillow to use this function"))
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+ if not output_file:
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+ output_file = input_file
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+ img = Image.open(input_file)
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+ img.thumbnail(size, Image.ANTIALIAS)
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+ img.save(output_file, format)
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+
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+
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+def change_rbg_to_transparent(input_file, output_file=None, color='white',
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+ alpha=0, format=None):
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+ """Make a specified RGB color in the image transparent
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+
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+ The color is specified as a RGB tuple (triplet) or string 'white'
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+ or 'black'. Note that GRASS color names are not supported.
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+ The white (255, 255, 255) is replaced by default but each application
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+ is encouraged to consider color to use and explicitly specify it.
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+
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+ :param input_file: Name of the file to manipulate
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+ :param color: Color to be replaced by transparency (tuple of three ints)
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+ :param alpha: Level of opacity (0 fully transparent, 255 fully opaque)
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+ :param output_file: filename for the new file (same as input by default)
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+ :param format: format to be used new file (if different from extension)
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+ """
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+ if PIL is None:
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+ raise RuntimeError(_("Install PIL or Pillow to use this function"))
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+ if color == 'white':
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+ rgb = (255, 255, 255)
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+ elif color == 'black':
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+ rgb = (0, 0, 0)
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+ else:
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+ rgb = color # pylint: disable=redefined-variable-type
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+ if not output_file:
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+ output_file = input_file
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+ img = Image.open(input_file)
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+ img = img.convert("RGBA")
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+ old_data = img.getdata()
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+ new_data = []
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+ for item in old_data:
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+ if item[0] == rgb[0] and item[1] == rgb[1] and item[2] == rgb[2]:
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+ new_data.append((rgb[0], rgb[1], rgb[2], alpha))
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+ else:
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+ new_data.append(item)
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+ img.putdata(new_data)
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+ img.save(output_file, format)
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+
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+
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+def invert_image_colors(input_file, output_file=None, format=None):
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+ """Invert colors in the image
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+
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+ The alpha channel, if present, is untouched by this function.
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+
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+ :param input_file: Name of the file to manipulate
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+ :param output_file: filename for the new file (same as input by default)
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+ :param format: format to be used new file (if different from extension)
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+ """
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+ if PIL is None:
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+ raise RuntimeError(_("Install PIL or Pillow to use this function"))
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+ if ImageOps is None:
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+ raise RuntimeError(_("Install a newer version of PIL or Pillow to"
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+ " use this function (missing ImageOps module)"))
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+ if not output_file:
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+ output_file = input_file
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+ original_img = Image.open(input_file)
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+ # according to documentation (3.0.x) the module can work only on RGB
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+ # so we need to specifically take care of transparency if present
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+ if original_img.mode == 'RGBA':
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+ # split into bands
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+ red1, green1, blue1, alpha = original_img.split()
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+ rgb_img = Image.merge('RGB', (red1, green1, blue1))
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+ # invert RGB
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+ inverted_rgb_img = ImageOps.invert(rgb_img)
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+ # put back the original alpha
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+ red2, green2, blue2 = inverted_rgb_img.split()
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+ new_image = Image.merge('RGBA', (red2, green2, blue2, alpha))
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+ else:
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+ new_image = ImageOps.invert(original_img)
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+ new_image.save(output_file, format)
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Vaclav Petras