应用发动机裁剪到特定的宽度和高度
题
我需要将图像调整并裁剪到特定的宽度和高度。我能够构建一种将创建正方形缩略图的方法,但是当所需的缩略图不是正方形时,我不确定如何应用此方法。
def rescale(data, width, height):
"""Rescale the given image, optionally cropping it to make sure the result image has the specified width and height."""
from google.appengine.api import images
new_width = width
new_height = height
img = images.Image(data)
org_width, org_height = img.width, img.height
# We must determine if the image is portrait or landscape
# Landscape
if org_width > org_height:
# With the Landscape image we want the crop to be centered. We must find the
# height to width ratio of the image and Convert the denominater to a float
# so that ratio will be a decemal point. The ratio is the percentage of the image
# that will remain.
ratio = org_height / float(org_width)
# To find the percentage of the image that will be removed we subtract the ratio
# from 1 By dividing this number by 2 we find the percentage that should be
# removed from each side this is also our left_x coordinate
left_x = (1- ratio) / 2
# By subtract the left_x from 1 we find the right_x coordinate
right_x = 1 - left_x
# crop(image_data, left_x, top_y, right_x, bottom_y), output_encoding=images.PNG)
img.crop(left_x, 0.0, right_x, 1.0)
# resize(image_data, width=0, height=0, output_encoding=images.PNG)
img.resize(height=height)
# Portrait
elif org_width < org_height:
ratio = org_width / float(org_height)
# crop(image_data, left_x, top_y, right_x, bottom_y), output_encoding=images.PNG)
img.crop(0.0, 0.0, 1.0, ratio)
# resize(image_data, width=0, height=0, output_encoding=images.PNG)
img.resize(width=witdh)
thumbnail = img.execute_transforms()
return thumbnail
如果有更好的方法来做到这一点,请告诉我。任何帮助将不胜感激。
这是解释所需过程的图。
谢谢,
凯尔
解决方案
我也有类似的问题(您的屏幕截图非常有用)。这是我的解决方案:
def rescale(img_data, width, height, halign='middle', valign='middle'):
"""Resize then optionally crop a given image.
Attributes:
img_data: The image data
width: The desired width
height: The desired height
halign: Acts like photoshop's 'Canvas Size' function, horizontally
aligning the crop to left, middle or right
valign: Verticallly aligns the crop to top, middle or bottom
"""
image = images.Image(img_data)
desired_wh_ratio = float(width) / float(height)
wh_ratio = float(image.width) / float(image.height)
if desired_wh_ratio > wh_ratio:
# resize to width, then crop to height
image.resize(width=width)
image.execute_transforms()
trim_y = (float(image.height - height) / 2) / image.height
if valign == 'top':
image.crop(0.0, 0.0, 1.0, 1 - (2 * trim_y))
elif valign == 'bottom':
image.crop(0.0, (2 * trim_y), 1.0, 1.0)
else:
image.crop(0.0, trim_y, 1.0, 1 - trim_y)
else:
# resize to height, then crop to width
image.resize(height=height)
image.execute_transforms()
trim_x = (float(image.width - width) / 2) / image.width
if halign == 'left':
image.crop(0.0, 0.0, 1 - (2 * trim_x), 1.0)
elif halign == 'right':
image.crop((2 * trim_x), 0.0, 1.0, 1.0)
else:
image.crop(trim_x, 0.0, 1 - trim_x, 1.0)
return image.execute_transforms()
其他提示
您可以同时指定 height
和 width
参数为 resize
- 它不会改变纵横比(您不能使用GAE的 images
模块),但它将确保两个维度中的每个维度是 <=
您指定的相应值(实际上,一个将完全等于您指定的值,另一个将是 <=
).
我不确定为什么要首先裁剪并以后进行调整 - 似乎您应该以相反的方式做事...调整大小,以使原始图像“合适”尽可能可行,然后裁剪以确保确切的结果尺寸。 (因此,您不会为调整大小的原始提供的高度和宽度值使用 - 如果我正确理解您的要求,则不会将结果图像浪费在“又称“空白”)。因此,也许我不完全理解您的要求 - 您可以提供一个示例(在处理前的图像时,图像的URL,处理后的外观以及您要传递的参数的详细信息) ?
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