Source code for jpegtran.transform

from __future__ import division

import re

import jpegtran.lib as lib

[docs]class JPEGImage(object):
[docs] def __init__(self, fname=None, blob=None): """ Initialize the image with either a filename or a string or bytearray containing the JPEG image data. :param fname: Filename of JPEG file :type fname: str :param blob: JPEG image data :type blob: str/bytearray """ if (not fname and not blob) or (fname and blob): raise Exception("Must initialize with either fname or blob.") if fname is not None: with open(fname, 'rb') as fp: = bytearray( elif blob is not None: = bytearray(blob)
@property def width(self): """ Width of the image in pixels. """ return lib.Transformation([0] @property def height(self): """ Height of the image in pixels. """ return lib.Transformation([1] @property def exif_thumbnail(self): """ EXIF thumbnail. :return: EXIF thumbnail in JPEG format :rtype: str """ try: return JPEGImage(blob=lib.Exif( except lib.ExifException: return None @exif_thumbnail.setter def exif_thumbnail(self, image): if isinstance(image, JPEGImage): data = elif isinstance(image, str): data = bytearray(image) else: data = image if not self.exif_thumbnail: raise ValueError("No pre-existing thumbnail found, cannot set.") lib.Exif( = data @property def exif_orientation(self): """ Exif orientation value as a number between 1 and 8. Property is read/write """ try: return lib.Exif( except lib.ExifException: return None @exif_orientation.setter def exif_orientation(self, value): if not 0 < value < 9: raise ValueError("Orientation value must be between 1 and 8") lib.Exif( = value
[docs] def exif_autotransform(self): """ Automatically transform the image according to its EXIF orientation tag. :return: transformed image :rtype: jpegtran.JPEGImage """ orient = self.exif_orientation if orient is None: raise Exception("Could not find EXIF orientation") elif orient == 1: return self elif orient == 2: return self.flip('horizontal') elif orient == 3: return self.rotate(180) elif orient == 4: return self.flip('vertical') elif orient == 5: return self.transpose() elif orient == 6: return self.rotate(90) elif orient == 7: return self.transverse() elif orient == 8: return self.rotate(270)
[docs] def rotate(self, angle): """ Rotate the image. :param angle: rotation angle :type angle: -90, 90, 180 or 270 :return: rotated image :rtype: jpegtran.JPEGImage """ if angle not in (-90, 90, 180, 270): raise ValueError("Angle must be -90, 90, 180 or 270.") img = JPEGImage(blob=lib.Transformation( # Set EXIF orientation to 'Normal' (== no rotation) if img.exif_orientation not in (None, 1): img.exif_orientation = 1 img._update_thumbnail() return img
[docs] def flip(self, direction): """ Flip the image in horizontal or vertical direction. :param direction: Flipping direction :type direction: 'vertical' or 'horizontal' :return: flipped image :rtype: jpegtran.JPEGImage """ if direction not in ('horizontal', 'vertical'): raise ValueError("Direction must be either 'vertical' or " "'horizontal'") new = JPEGImage(blob=lib.Transformation( new._update_thumbnail() return new
[docs] def transpose(self): """ Transpose the image (across upper-right -> lower-left axis) :return: transposed image :rtype: jpegtran.JPEGImage """ new = JPEGImage(blob=lib.Transformation( new._update_thumbnail() return new
[docs] def transverse(self): """ Transverse transpose the image (across upper-left -> lower-right axis) :return: transverse transposed image :rtype: jpegtran.JPEGImage """ new = JPEGImage(blob=lib.Transformation( new._update_thumbnail() return new
[docs] def crop(self, x, y, width, height): """ Crop a rectangular area from the image. :param x: horizontal coordinate of upper-left corner :type x: int :param y: vertical coordinate of upper-left corner :type y: int :param width: width of area :type width: int :param height: height of area :type height: int :return: cropped image :rtype: jpegtran.JPEGImage """ valid_crop = (x < self.width and y < self.height and x+width <= self.width and y+height <= self.height) if not valid_crop: raise ValueError("Crop parameters point outside of the image") new = JPEGImage(blob=lib.Transformation( .crop(x, y, width, height)) new._update_thumbnail() return new
[docs] def downscale(self, width, height, quality=75): """ Downscale the image. :param width: Scaled image width :type width: int :param height: Scaled image height :type height: int :param quality: JPEG quality of scaled image (default: 75) :type quality: int :return: downscaled image :rtype: jpegtran.JPEGImage """ if width == self.width and height == self.height: return self if width > self.width or height > self.height: raise ValueError("jpegtran can only downscale JPEGs") new = JPEGImage(blob=lib.Transformation( .scale(width, height, quality)) new._update_thumbnail() return new
[docs] def save(self, fname): """ Save the image to a file :param fname: Path to file :type fname: unicode """ if not re.match(r'^.*\.jp[e]*g$', fname.lower()): raise ValueError("fname must refer to a JPEG file, i.e. end with " "'.jpg' or '.jpeg'") with open(fname, 'wb') as fp: fp.write(
[docs] def as_blob(self): """ Get the image data as a string :return: Image data :rtype: bytes """ return bytes(
def _update_thumbnail(self): if not self.exif_thumbnail: return target_width = None target_height = None if self.width > self.height: target_width = 160 target_height = int(160/(self.width/self.height)) else: target_height = 160 target_width = int(160*(self.width/self.height)) if target_width > self.width and target_height > self.height: # TODO: We should instead strip the thumbnail completely since # it clearly no longer makes any sense return updated = self.downscale(target_width, target_height) self.exif_thumbnail = updated