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Improved method for calculating the crop box on images with focal points

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This commit is contained in:
Karl Hobley 2014-09-15 17:33:34 +01:00
parent b7ac3042c4
commit c974975590
1 changed files with 66 additions and 25 deletions
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91
wagtail/wagtailimages/backends/base.py
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@ -133,7 +133,7 @@ class BaseImageBackend(object):
if original_height <= target_height:
return image
scale = target_height / original_height
scale = target_height / original_hight
final_size = (int(original_width * scale), target_height)
@ -157,34 +157,75 @@ class BaseImageBackend(object):
else:
crop_closeness = 0
if focal_point is not None and crop_closeness > 0:
# Get focal point as a rect
left = focal_point.x - focal_point.width / 2
top = focal_point.y - focal_point.height / 2
right = focal_point.x + focal_point.width / 2
bottom = focal_point.y + focal_point.height / 2
# Get image width and height
(im_width, im_height) = image.size
# Interpolate focal point rect with the images original size by crop closeness
# When crop_closeness = 0: new FP = image size
# When crop_closeness = 1: new FP = original FP size
(original_width, original_height) = image.size
left = left * crop_closeness
top = top * crop_closeness
right = (right - original_width) * crop_closeness + original_width
bottom = (bottom - original_height) * crop_closeness + original_height
# Get filter width and height
fl_width = size[0]
fl_height = size[1]
# Create new focal point
new_x = (left + right) / 2
new_y = (top + bottom) / 2
new_width = right - left
new_height = bottom - top
new_focal_point = FocalPoint(new_x, new_y, width=new_width, height=new_height)
# Get crop aspect ratio
crop_aspect_ratio = fl_width / fl_height
# Crop
return self.crop_to_point(image, size, new_focal_point)
# Get crop max
crop_max_scale = min(im_width, im_height * crop_aspect_ratio)
crop_max_width = crop_max_scale
crop_max_height = crop_max_scale / crop_aspect_ratio
# Initialise crop width and height to max
crop_width = crop_max_width
crop_height = crop_max_height
# Use crop closeness to zoom in
if focal_point is not None:
fp_width = focal_point.width
fp_height = focal_point.height
# Get crop min
crop_min_scale = max(fp_width, fp_height * crop_aspect_ratio)
crop_min_width = crop_min_scale
crop_min_height = crop_min_scale / crop_aspect_ratio
# Sometimes, the focal point may be bigger than the image...
if not crop_min_scale > crop_max_scale:
# Calculate max crop closeness to prevent upscaling
max_crop_closeness = max(
1 - (fl_width - crop_min_width) / (crop_max_width - crop_min_width),
1 - (fl_height - crop_min_height) / (crop_max_height - crop_min_height)
)
# Apply max crop closeness
crop_closeness = min(crop_closeness, max_crop_closeness)
# Get crop width and height
crop_width = crop_max_width + (crop_min_width - crop_max_width) * crop_closeness
crop_height = crop_max_height + (crop_min_height - crop_max_height) * crop_closeness
# Find focal point UV
if focal_point is not None:
fp_x = focal_point.x
fp_y = focal_point.y
else:
resized_image = self.resize_to_min(image, size)
return self.crop_to_centre(resized_image, size)
# Fall back to positioning in the centre
fp_x = im_width / 2
fp_y = im_height / 2
fp_u = fp_x / im_width
fp_v = fp_y / im_height
# Position crop box based on focal point UV
crop_x = fp_x - (fp_u - 0.5) * crop_width
crop_y = fp_y - (fp_v - 0.5) * crop_height
# Convert crop box into rect
left = crop_x - crop_width / 2
top = crop_y - crop_height / 2
right = crop_x + crop_width / 2
bottom = crop_y + crop_height / 2
# Crop!
return self.resize_to_min(self.crop(image, crop.CropBox(left, top, right, bottom)), size)
def no_operation(self, image, param, focal_point=None):
"""Return the image unchanged"""