Dump Image Pixels into vector from coordinates

2 次查看（过去 30 天）
Philip
Philip 2012-4-16
Is there a way to use 2 vectors of pixel coordinates to quickly dump the pixel values into a 3rd vector?
Currently, I am using the following for loop, but it is very slow:
for j=1:length(x)
pixel_vals(j) = img(x(j),y(j));
end
where, 'x' and 'y' are the x,y coordinates (1xN vector form).
Many thanks!

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2012-4-16
pixel_vals = img(subs2ind(size(x), x, y));

更多回答（2 个）

Image Analyst
Image Analyst 2012-4-16
Philip, in response to the new question in your "Answer" (not your original question), the preferred way to do this is with ismember(). Your way would take forever for an image with lots of pixels that have labels. See this code snippet from my image segmentation tutorial, BlobsDemo: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862
% Extract only those blobs that meet our criteria, and
% eliminate those blobs that don't meet our criteria.
% Note how we use ismember() to do this.
keeperBlobsImage = ismember(labeledImage, keeperIndexes);
% Re-label with only the keeper blobs kept.
labeledDimeImage = bwlabel(keeperBlobsImage, 8); % Label each blob so we can make measurements of it
Philip
Philip 2012-4-16
On a similar note, is there any way that I can replace the following loop:
label_ids = [1 3 11 24 55];
map = zeros(height_img, width_img);
for i=1:length(label_ids)
map = BWlabel_img==label_ids(i) + map;
end
The label_ids correspond to line segments in a 'bwlabel' image that I want to keep. Essentially, I want to create a new image 'map' that contains only the line segments with these id numbers...
  1 个评论
Image Analyst
Image Analyst 2012-4-16
This should have been a new question, not an answer. Comments can't have formatted code, so see my answer below.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Image Arithmetic 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by