[1] | 1 | from cStringIO import StringIO |
---|
| 2 | |
---|
| 3 | from PIL import Image |
---|
| 4 | |
---|
| 5 | |
---|
| 6 | |
---|
| 7 | # Settings for member image resize quality |
---|
| 8 | PIL_SCALING_ALGO = Image.ANTIALIAS |
---|
| 9 | PIL_QUALITY = 88 |
---|
| 10 | MEMBER_IMAGE_SCALE = (75, 100) |
---|
| 11 | |
---|
| 12 | def scale_image(image_file, max_size=MEMBER_IMAGE_SCALE, |
---|
| 13 | default_format = 'PNG'): |
---|
| 14 | """Scales an image down to at most max_size preserving aspect ratio |
---|
| 15 | from an input file |
---|
| 16 | |
---|
| 17 | >>> import Products.CMFPlone |
---|
| 18 | >>> import os |
---|
| 19 | >>> from StringIO import StringIO |
---|
| 20 | >>> from Products.CMFPlone.utils import scale_image |
---|
| 21 | >>> from PIL import Image |
---|
| 22 | |
---|
| 23 | Let's make a couple test images and see how it works (all are |
---|
| 24 | 100x100), the gif is palletted mode:: |
---|
| 25 | |
---|
| 26 | >>> plone_path = os.path.dirname(Products.CMFPlone.__file__) |
---|
| 27 | >>> pjoin = os.path.join |
---|
| 28 | >>> path = pjoin(plone_path, 'tests', 'images') |
---|
| 29 | >>> orig_jpg = open(pjoin(path, 'test.jpg')) |
---|
| 30 | >>> orig_png = open(pjoin(path, 'test.png')) |
---|
| 31 | >>> orig_gif = open(pjoin(path, 'test.gif')) |
---|
| 32 | |
---|
| 33 | We'll also make some evil non-images, including one which |
---|
| 34 | masquerades as a jpeg (which would trick OFS.Image):: |
---|
| 35 | |
---|
| 36 | >>> invalid = StringIO('<div>Evil!!!</div>') |
---|
| 37 | >>> sneaky = StringIO('\377\330<div>Evil!!!</div>') |
---|
| 38 | |
---|
| 39 | OK, let's get to it, first check that our bad images fail: |
---|
| 40 | |
---|
| 41 | >>> scale_image(invalid, (50, 50)) |
---|
| 42 | Traceback (most recent call last): |
---|
| 43 | ... |
---|
| 44 | IOError: cannot identify image file |
---|
| 45 | >>> scale_image(sneaky, (50, 50)) |
---|
| 46 | Traceback (most recent call last): |
---|
| 47 | ... |
---|
| 48 | IOError: cannot identify image file |
---|
| 49 | |
---|
| 50 | Now that that's out of the way we check on our real images to make |
---|
| 51 | sure the format and mode are preserved, that they are scaled, and that they |
---|
| 52 | return the correct mimetype:: |
---|
| 53 | |
---|
| 54 | >>> new_jpg, mimetype = scale_image(orig_jpg, (50, 50)) |
---|
| 55 | >>> img = Image.open(new_jpg) |
---|
| 56 | >>> img.size |
---|
| 57 | (50, 50) |
---|
| 58 | >>> img.format |
---|
| 59 | 'JPEG' |
---|
| 60 | >>> mimetype |
---|
| 61 | 'image/jpeg' |
---|
| 62 | |
---|
| 63 | >>> new_png, mimetype = scale_image(orig_png, (50, 50)) |
---|
| 64 | >>> img = Image.open(new_png) |
---|
| 65 | >>> img.size |
---|
| 66 | (50, 50) |
---|
| 67 | >>> img.format |
---|
| 68 | 'PNG' |
---|
| 69 | >>> mimetype |
---|
| 70 | 'image/png' |
---|
| 71 | |
---|
| 72 | >>> new_gif, mimetype = scale_image(orig_gif, (50, 50)) |
---|
| 73 | >>> img = Image.open(new_gif) |
---|
| 74 | >>> img.size |
---|
| 75 | (50, 50) |
---|
| 76 | >>> img.format |
---|
| 77 | 'GIF' |
---|
| 78 | >>> img.mode |
---|
| 79 | 'P' |
---|
| 80 | >>> mimetype |
---|
| 81 | 'image/gif' |
---|
| 82 | |
---|
| 83 | We should also preserve the aspect ratio by scaling to the given |
---|
| 84 | width only unless told not to (we need to reset out files before |
---|
| 85 | trying again though:: |
---|
| 86 | |
---|
| 87 | >>> orig_jpg.seek(0) |
---|
| 88 | >>> new_jpg, mimetype = scale_image(orig_jpg, (70, 100)) |
---|
| 89 | >>> img = Image.open(new_jpg) |
---|
| 90 | >>> img.size |
---|
| 91 | (70, 70) |
---|
| 92 | |
---|
| 93 | >>> orig_jpg.seek(0) |
---|
| 94 | >>> new_jpg, mimetype = scale_image(orig_jpg, (70, 50)) |
---|
| 95 | >>> img = Image.open(new_jpg) |
---|
| 96 | >>> img.size |
---|
| 97 | (50, 50) |
---|
| 98 | |
---|
| 99 | """ |
---|
| 100 | # Make sure we have ints |
---|
| 101 | size = (int(max_size[0]), int(max_size[1])) |
---|
| 102 | # Load up the image, don't try to catch errors, we want to fail miserably |
---|
| 103 | # on invalid images |
---|
| 104 | image = Image.open(image_file) |
---|
| 105 | # When might image.format not be true? |
---|
| 106 | format = image.format |
---|
| 107 | mimetype = 'image/%s'%format.lower() |
---|
| 108 | cur_size = image.size |
---|
| 109 | # from Archetypes ImageField |
---|
| 110 | # consider image mode when scaling |
---|
| 111 | # source images can be mode '1','L,','P','RGB(A)' |
---|
| 112 | # convert to greyscale or RGBA before scaling |
---|
| 113 | # preserve palletted mode (but not pallette) |
---|
| 114 | # for palletted-only image formats, e.g. GIF |
---|
| 115 | # PNG compression is OK for RGBA thumbnails |
---|
| 116 | original_mode = image.mode |
---|
| 117 | if original_mode == '1': |
---|
| 118 | image = image.convert('L') |
---|
| 119 | elif original_mode == 'P': |
---|
| 120 | image = image.convert('RGBA') |
---|
| 121 | # Rescale in place with an method that will not alter the aspect ratio |
---|
| 122 | # and will only shrink the image not enlarge it. |
---|
| 123 | image.thumbnail(size, resample=PIL_SCALING_ALGO) |
---|
| 124 | # preserve palletted mode for GIF and PNG |
---|
| 125 | if original_mode == 'P' and format in ('GIF', 'PNG'): |
---|
| 126 | image = image.convert('P') |
---|
| 127 | # Save |
---|
| 128 | new_file = StringIO() |
---|
| 129 | image.save(new_file, format, quality=PIL_QUALITY) |
---|
| 130 | new_file.seek(0) |
---|
| 131 | # Return the file data and the new mimetype |
---|
| 132 | return new_file, mimetype |
---|
| 133 | |
---|