From 890f74a7f491d1f7b1d50155469f26a17be8eb1d Mon Sep 17 00:00:00 2001 From: Nick White Date: Tue, 17 Dec 2019 18:03:26 +0000 Subject: WIP adaptive binarisation --- content/posts/adaptive-binarisation/index.md | 27 +++++++++++++++++++++++- content/posts/binarisation-introduction/index.md | 4 ++-- 2 files changed, 28 insertions(+), 3 deletions(-) (limited to 'content/posts') diff --git a/content/posts/adaptive-binarisation/index.md b/content/posts/adaptive-binarisation/index.md index 0060f44..4266343 100644 --- a/content/posts/adaptive-binarisation/index.md +++ b/content/posts/adaptive-binarisation/index.md @@ -1,6 +1,31 @@ --- title: "Adaptive Binarisation" -date: 2019-10-02 +date: 2019-12-17 draft: true categories: [binarisation, preprocessing, image manipulation] --- +The [previous post](/posts/binarisation-introduction) covered the +basics of binarisation, and introduced the Otsu algorithm, a good +method for finding a global threshold number for a page. But there +are inevitable limitations with using a global threshold for +binarisation. Better would be to use a threshold that is adapted +over different regions of the page, so that as the conditions of the +page change so can the threshold. This technique is called adaptive +binarisation. + +For each pixel of an image, adaptive binarisation considers the +pixels around it to determine a good threshold. This means that even +in an area which is heavily shaded, for example near the spine of a +book, the text will be correctly differentiated from the background, +as even though they may both be darker than the text in the rest of +the page, it is the darkness relative to its surroundings that +matters. + + diff --git a/content/posts/binarisation-introduction/index.md b/content/posts/binarisation-introduction/index.md index 13b27dc..288637c 100644 --- a/content/posts/binarisation-introduction/index.md +++ b/content/posts/binarisation-introduction/index.md @@ -73,5 +73,5 @@ than the global threshold. Both of these criticisms could be addressed by using an algorithm that could alter the threshold according to the conditions of the region on -the page. That will be covered in the next blog post. +the page. That will be covered in the next blog post, +[Adaptive Binarisation](/posts/adaptive-binarisation). -- cgit v1.2.1-24-ge1ad