How to centralize alphabets in an image?

Question

Ihtisham Khan 2018-4-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394971-how-to-centralize-alphabets-in-an-image

评论： Walter Roberson 2018-4-15

Hello,

I have an 80x80 image that contains an Arabic alphabet (black pixels) against white background. The alphabet is dislocated from the center of the image. The idea is to centralize the alphabet in the image. As I have many alphabets, the algorithm should do the same for other alphabets.

Demo image is here,

Your help is highly appreciated.

Thanks.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2018-4-15

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394971-how-to-centralize-alphabets-in-an-image#answer_315169

在 MATLAB Online 中打开

regionprops() of imcomplement() of the image, requesting 'SubarrayIdx', and use those to access the image.

Note: you should also consider regionprops() of imcomplement() of the image, requesting 'Image' . You could use this if you are not interested in analyzing grayscale levels, just on/off

Note: if your image is binary, and your characters can have disconnected parts, then

regionprops(double(~BinaryImage), ...)

This prevents regionprops from considering each disconnected component separately.

Note: I am not familiar with the rules for Arabic, but in a number of other alphabets, the position of a character relative to the base-line can make a difference in the meaning of the character. For example in some languages a dot near the base-line is a period (punctuation) but a raised dot can indicate an accent or a vowel mark. Because of that, it is sometimes important to either not center the object, or else to also retain information about the object position for later testing against the base-line coordinates.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Ihtisham Khan 2018-4-15

Thanks a lot Walter Roberson , your answer cleared my concept.

请先登录，再进行评论。

Answer 2

Image Analyst 2018-4-15

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394971-how-to-centralize-alphabets-in-an-image#answer_315224

在 MATLAB Online 中打开

I'd threshold and use regionprops() to find the centroid of the character.

binaryImage = grayImage < 128;
binaryImage = bwareafilt(binaryImage, 1);
props = regionprops(binaryImage, 'Centroid');
xCentroid = props.Centroid(1);
yCentroid = props.Centroid(2);

Then I'd use circshift() or imtranslate() to move the character centroid to the middle of the image.

[rows, columns] = size(binaryImage);
middleRow = rows/2;
middleColumn = columns/2;

etc.

2 个评论
显示无隐藏无

Ihtisham Khan 2018-4-15

Thats OK, but for alphabets with disconnected parts regionprops calculates more than one center. How to fix that.

Walter Roberson 2018-4-15

在 MATLAB Online 中打开

props = regionprops(double(binaryImage), 'Centroid');

请先登录，再进行评论。