MATLAB: How I convert all points above a line from 0 to 1

matrix manipulation

The red points represent the line (hLine).

I want convert all points above the red line from 0 to 1.

Best Answer

If the lines were strictly diagonal, then you could make use of tril or triu. For example,

max(Data, triu(ones(size(Data)),-3) )

With non-diagonal lines, then consider using poly2mask. You will need to take into account https://www.mathworks.com/help/images/ref/poly2mask.html#bq508ot

"To specify a polygon that includes a given rectangular set of pixels, make the edges of the polygon lie along the outside edges of the bounding pixels, instead of the center of the pixels."

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MATLAB: How to find the broadest width of contour and calculate it.

Try this (untested)

binaryImage = grayImage >= 1440
binaryImage = bwareafilt(binaryImage, 1); % Extract only the largest blob.
[rows, columns] = size(binaryImage);
for col = 1 : columns
        thisColumn = binaryImage(:, col);
        topRow(col) = find(thisColumn, 1, 'first');
        bottomRow(col)= find(thisColumn, 1, 'last');
        heights(col) = bottomRow(col) - topRow(col);
end
maxHeight = max(heights);
columnsOfMaxHeight = find(heights == maxHeight); % Might be more than one column with max height!
% Draw it
hold on;
for k = 1 : length(columnsOfMaxHeight)
        thisCol = columnsOfMaxHeight(k);
        line([thisCol, thisCol], [topRow(thisCol), bottomRow(thisCol)], 'Color', 'r', 'LineWidth', 2)
end

Let me know of any problems.

MATLAB: How to make all pixels under an assisted line boundary = 1

Try this (untested) with your mask to create a mask where the lower portion is true and the upper portion is false.:

[rows, columns] = size(mask); % Get size of your binary image with the line in it.
lastRow = ones(1, columns); % Initialize to top of image.
% Initialize a lower mask
lowerMask = false(rows, columns);
% Scan columns finding the last
for col = 1 : columns
    thisColumn = mask(:, col);
    t = find(thisColumn, 1, 'last');
    if ~isempty(t)
        lastRow(col) = t;
    end
    lowerMask(lastRow(col) : end, col) = true;
end
imshow(lowerMask);

Best Answer

Related Solutions

MATLAB: How to find the broadest width of contour and calculate it.

MATLAB: How to make all pixels under an assisted line boundary = 1

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