Draw 1 inch Square on Image

Hello,

How can I draw 1 inch square on my image and wanted to find number of grains present in that square ? Attached is my Image for reference. In attached RefImage_WithSquare, wanted to count no. of grains present in that square grains on boundary line must be considered as partial grain. Just as we consider in ASTM Grain Analysis.

[Rik]

This question is unlikely to get responses for several reasons: you didn't include the image in the first place, any size information is not present (how should pixels be translated to inches), it is unclear what you mean by grains and how they should be counted, and you show nothing about what you already start.

We have nothing to build on, and we have no indication that you care enough to put in some effort. Have a read here (or here for more general advice) and here. It will greatly improve your chances of getting an answer.

You can edit your question to fix these issues, which will automatically re-open your question.

[Parth Desai]

Updated my question with attached images for reference.

Answer 1

[Image Analyst]

If your resolution is 96 dpi, use the rectangle() function with a width and height of 96:

imshow('untitled.png');
axis on;
hold on;
impixelinfo(); % Show x, y, RGB as you mouse around over image.
xLeft = 85; % Wherever you want.
yTop = 32;
rectangle('Position', [xLeft, yTop, 96, 96], 'EdgeColor', 'r', 'LineWidth', 2);

[Parth Desai]

Hello, Thanks but how can i find out the grains count in that square.

[Image Analyst]

You can use bwlabel(). By the way, why did you not answer my question about partial blobs?

[rows, columns, numColors] = size(yourImage);
if numColors == 3
    yourImage = rgb2gray(yourImage);
end
subImage = yourImage(yTop:yTop+95, xLeft:xLeft+95);
binaryImage = subImage ~= 255; % Or whatever color your background is.
% Count blobs and partial blobs.
[labeledImage, numBlobs] = bwlabel(binaryImage);

If you want to remove blobs touching the border, call imclearborder() before you call bwlabel.

binaryImage = imclearborder(binaryImage);

[Parth Desai]

This will count blobs in my image but I want to count blobs present in the rectangle. why did you not answer my question about partial blobs? blobs touching the boundary of rectangle to be considered as half blob.

[Image Analyst]

No, it will count only blobs that are in the subImage, which is the rectangular ROI, not the entire original image.

No one ever counts blobs as half a blob. That doesn't make sense. If you want an area fraction, you can get that by

areaFraction = sum(binaryImage)/numel(binaryImage);

[Parth Desai]

Error Undefined function 'yourImage' for input arguments of type 'double'.

Error in Dummy_0 (line 86) subImage = yourImage(yTop:yTop+95, xLeft:xLeft+95);

      imshow('Output.png');
  axis on;
  hold on;
  impixelinfo(); % Show x, y, RGB as you mouse around over image.
  xLeft = 85; % Wherever you want.
  yTop = 32;
  rectangle('Position', [xLeft, yTop, 96, 96], 'EdgeColor', 'r', 'LineWidth', 2);

[rows, columns, numColors] = size('Output.png');
if numColors == 3
    yourImage = rgb2gray('Output.png');
end
subImage = yourImage(yTop:yTop+95, xLeft:xLeft+95);
binaryImage = subImage ~= 255; % Or whatever color your background is.
% Count blobs and partial blobs.
[labeledImage, numBlobs] = bwlabel(binaryImage);

[Image Analyst]

Parth, you need to read your image into a variable.

Do this:

yourImage = imread('Output.png');
imshow(yourImage);
[rows, columns, numColors] = size(yourImage);