如何使用PIL Image.point(table)方法将阈值应用于256灰度图像? [英] How to I use PIL Image.point(table) method to apply a threshold to a 256 gray image?

问题描述

我有8位灰度TIFF图像，我想使用75％的白色(十进制190)阈值转换为单色.在Image.convert(mode)方法部分中，PIL手册说:

I have 8-bit greyscale TIFF images that I want to convert to Monochrome using a 75% white (decimal 190) threshold. In the Image.convert(mode) method section, the PIL manual says:

将灰度图像转换为位图像(模式"1")时，所有非零值均设置为255(白色).要使用其他阈值，请使用点方法."

"When translating a greyscale image into a bitlevel image (mode "1"), all non-zero values are set to 255 (white). To use other thresholds, use the point method."

Image.point(table)方法表示它会映射给定表中的每个像素.

The Image.point(table) method says that it maps each pixel through the given table.

im.point(表格，模式)=>图片
im.point(功能，模式)=>图片

im.point(table, mode) => image
im.point(function, mode) => image

通过表格映射图像，并进行即时转换.在PIL的当前版本中，这只能用于一步将'L'和'P'图像转换为'1'，例如将阈值限制为图片."

"Map the image through table, and convert it on fly. In the current version of PIL , this can only be used to convert 'L' and 'P' images to '1' in one step, e.g. to threshold an image."

如何创建与我所需的75％阈值相对应的表(或函数)?

How do I create the table (or function) that corresponds to the 75% threshold I need?

推荐答案

我在此答案中找到了完整的解决方案"

I found the complete solution in this answer "Write TIFF file in python from String". The function must include "and 255"

threshold = 191  
im = im.point(lambda p: p > threshold and 255)  

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