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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