stuartl/tornado-gallery
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resizer: Ensure aspect ratio is maintained.

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Implement a function that computes the aspect ratio and scales the width
or height automatically to fit the bounding box given.

Re-implement scaling algorithm using this function.
This commit is contained in:
Stuart Longland 2018-04-30 21:19:09 +10:00
parent 7f17501c57
commit 8970021396
Signed by: stuartl
GPG Key ID: 6AA32EFB18079BAA
1 changed files with 47 additions and 16 deletions
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63
tornado_gallery/resizer.py
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@ -47,6 +47,39 @@ class ImageFormat(Enum):
return _FORMAT_PIL[self.value]
def calc_dimensions(raw_width, raw_height, width=None, height=None):
"""
Given the raw dimensions of a photo, and optional target dimensions,
return the dimensions of a photo that will fit in the target dimensions
whilst respecting the aspect ratio of the photo.
"""
# Simple case, neither given, do not scale.
if (width is None) and (height is None):
return (raw_width, raw_height)
# Compute aspect ratio
ratio = float(raw_width) / float(raw_height)
# Simple case: one dimension only given
if width is None:
# Scale by height only.
return (int(height * ratio), height)
elif height is None:
# Scale by width only.
return (width, int(width / ratio))
else:
# Both dimensions, pick the one that fits!
scaled_height = int(width / ratio)
scaled_width = int(height * ratio)
if scaled_width > width:
# Scale-by-height is too wide, scale-by-width.
return (width, scaled_height)
else:
# Scale-by-width is too tall, scale-by-height.
return (scaled_width, height)
class ResizerPool(object):
def __init__(self, root_dir_node, cache_subdir, num_proc=None, log=None):
if log is None:
@ -93,20 +126,10 @@ class ResizerPool(object):
self._log.debug('%s/%s using %s format',
gallery, photo, img_format.name)
# Do we need to compute full dimensions?
if (width is None) or (height is None):
raw_width, raw_height = yield self.get_dimensions(gallery, photo)
ratio = float(raw_width) / float(raw_height)
if (ratio >= 1.0) or (height is None):
# Fit to width
height = int(width / ratio)
else:
# Fit to height
width = int(height * ratio)
self._log.debug('%s/%s target dimensions %d by %d',
gallery, photo, width, height)
# Sanitise dimensions given by user.
width, height = self.get_dimensions(gallery, photo, width, height)
self._log.debug('%s/%s target dimensions %d by %d',
gallery, photo, width, height)
# Determine where the file would be cached
(cache_dir, cache_name) = self._get_cache_name(gallery, photo,
@ -251,14 +274,22 @@ class ResizerPool(object):
return (img_format, cache_name,
open(cache_path, 'rb').read())
def get_dimensions(self, gallery, photo, width=None, height=None):
img_node = self._fs_node.join_node(gallery, photo)
img = Image.open(open(img_node.abs_path,'rb'))
if (width is None) and (height is None):
return img.size
return calc_dimensions(*(img.size + (width, height)))
def get_properties(self, gallery, photo):
"""
Return the raw properties of the photo.
"""
log = self._log.getChild('%s/%s' % (gallery, photo))
img_node = self._fs_node.join_node(gallery, photo)
img = Image.open(open(img_node.abs_path,'rb'))
(width, height) = img.size
(width, height) = self.get_dimensions(gallery, photo)
meta = dict(width=width, height=height)
log.debug('Raw dimensions %dx%d', width, height)