[1] | 1 | from cStringIO import StringIO |
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| 2 | from PIL import Image |
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| 3 | |
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| 4 | # Settings for member image resize quality |
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| 5 | PIL_SCALING_ALGO = Image.ANTIALIAS |
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| 6 | PIL_QUALITY = 88 |
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| 7 | MEMBER_IMAGE_SCALE = (75, 100) |
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| 8 | |
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| 9 | def scale_image(image_file, max_size=MEMBER_IMAGE_SCALE, |
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| 10 | default_format = 'PNG'): |
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| 11 | """Scales an image down to at most max_size preserving aspect ratio |
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| 12 | from an input file |
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| 13 | |
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| 14 | >>> import Products.CMFPlone |
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| 15 | >>> import os |
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| 16 | >>> from StringIO import StringIO |
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| 17 | >>> from Products.CMFPlone.utils import scale_image |
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| 18 | >>> from PIL import Image |
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| 19 | |
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| 20 | Let's make a couple test images and see how it works (all are |
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| 21 | 100x100), the gif is palletted mode:: |
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| 22 | |
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| 23 | >>> plone_path = os.path.dirname(Products.CMFPlone.__file__) |
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| 24 | >>> pjoin = os.path.join |
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| 25 | >>> path = pjoin(plone_path, 'tests', 'images') |
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| 26 | >>> orig_jpg = open(pjoin(path, 'test.jpg')) |
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| 27 | >>> orig_png = open(pjoin(path, 'test.png')) |
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| 28 | >>> orig_gif = open(pjoin(path, 'test.gif')) |
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| 29 | |
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| 30 | We'll also make some evil non-images, including one which |
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| 31 | masquerades as a jpeg (which would trick OFS.Image):: |
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| 32 | |
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| 33 | >>> invalid = StringIO('<div>Evil!!!</div>') |
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| 34 | >>> sneaky = StringIO('\377\330<div>Evil!!!</div>') |
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| 35 | |
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| 36 | OK, let's get to it, first check that our bad images fail: |
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| 37 | |
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| 38 | >>> scale_image(invalid, (50, 50)) |
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| 39 | Traceback (most recent call last): |
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| 40 | ... |
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| 41 | IOError: cannot identify image file |
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| 42 | >>> scale_image(sneaky, (50, 50)) |
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| 43 | Traceback (most recent call last): |
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| 44 | ... |
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| 45 | IOError: cannot identify image file |
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| 46 | |
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| 47 | Now that that's out of the way we check on our real images to make |
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| 48 | sure the format and mode are preserved, that they are scaled, and that they |
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| 49 | return the correct mimetype:: |
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| 50 | |
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| 51 | >>> new_jpg, mimetype = scale_image(orig_jpg, (50, 50)) |
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| 52 | >>> img = Image.open(new_jpg) |
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| 53 | >>> img.size |
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| 54 | (50, 50) |
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| 55 | >>> img.format |
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| 56 | 'JPEG' |
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| 57 | >>> mimetype |
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| 58 | 'image/jpeg' |
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| 59 | |
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| 60 | >>> new_png, mimetype = scale_image(orig_png, (50, 50)) |
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| 61 | >>> img = Image.open(new_png) |
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| 62 | >>> img.size |
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| 63 | (50, 50) |
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| 64 | >>> img.format |
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| 65 | 'PNG' |
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| 66 | >>> mimetype |
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| 67 | 'image/png' |
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| 68 | |
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| 69 | >>> new_gif, mimetype = scale_image(orig_gif, (50, 50)) |
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| 70 | >>> img = Image.open(new_gif) |
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| 71 | >>> img.size |
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| 72 | (50, 50) |
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| 73 | >>> img.format |
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| 74 | 'GIF' |
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| 75 | >>> img.mode |
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| 76 | 'P' |
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| 77 | >>> mimetype |
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| 78 | 'image/gif' |
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| 79 | |
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| 80 | We should also preserve the aspect ratio by scaling to the given |
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| 81 | width only unless told not to (we need to reset out files before |
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| 82 | trying again though:: |
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| 83 | |
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| 84 | >>> orig_jpg.seek(0) |
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| 85 | >>> new_jpg, mimetype = scale_image(orig_jpg, (70, 100)) |
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| 86 | >>> img = Image.open(new_jpg) |
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| 87 | >>> img.size |
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| 88 | (70, 70) |
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| 89 | |
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| 90 | >>> orig_jpg.seek(0) |
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| 91 | >>> new_jpg, mimetype = scale_image(orig_jpg, (70, 50)) |
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| 92 | >>> img = Image.open(new_jpg) |
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| 93 | >>> img.size |
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| 94 | (50, 50) |
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| 95 | |
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| 96 | """ |
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| 97 | # Make sure we have ints |
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| 98 | size = (int(max_size[0]), int(max_size[1])) |
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| 99 | # Load up the image, don't try to catch errors, we want to fail miserably |
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| 100 | # on invalid images |
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| 101 | image = Image.open(image_file) |
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| 102 | # When might image.format not be true? |
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| 103 | format = image.format |
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| 104 | mimetype = 'image/%s'%format.lower() |
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| 105 | cur_size = image.size |
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| 106 | # from Archetypes ImageField |
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| 107 | # consider image mode when scaling |
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| 108 | # source images can be mode '1','L,','P','RGB(A)' |
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| 109 | # convert to greyscale or RGBA before scaling |
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| 110 | # preserve palletted mode (but not pallette) |
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| 111 | # for palletted-only image formats, e.g. GIF |
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| 112 | # PNG compression is OK for RGBA thumbnails |
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| 113 | original_mode = image.mode |
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| 114 | if original_mode == '1': |
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| 115 | image = image.convert('L') |
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| 116 | elif original_mode == 'P': |
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| 117 | image = image.convert('RGBA') |
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| 118 | # Rescale in place with an method that will not alter the aspect ratio |
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| 119 | # and will only shrink the image not enlarge it. |
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| 120 | image.thumbnail(size, resample=PIL_SCALING_ALGO) |
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| 121 | # preserve palletted mode for GIF and PNG |
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| 122 | if original_mode == 'P' and format in ('GIF', 'PNG'): |
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| 123 | image = image.convert('P') |
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| 124 | # Save |
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| 125 | new_file = StringIO() |
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| 126 | image.save(new_file, format, quality=PIL_QUALITY) |
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| 127 | new_file.seek(0) |
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| 128 | # Return the file data and the new mimetype |
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| 129 | return new_file, mimetype |
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| 130 | |
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