Coordinates of an object - Matlab - matlab

Question

How can I find the top, button, left, right x,y coordinates of this object?
Code:
clc;
clear all;
Image = rgb2gray(imread('https://upload-icon.s3.us-east-2.amazonaws.com/uploads/icons/png/1606078271536061993-512.png'));
BW = imbinarize(Image);
BW = imfill(BW,'holes');
BW = bwareaopen(BW, 100);
BW = padarray(BW,60,60,'both')
BW = imcomplement(BW);
imshow(BW)

Answer 1

The red pixels on the coordinate plot indicate the furthest most pixels to the left, right, top and bottom of the icon/image. This method similarly uses for-loops and break() statements to scan the image until a pixel of logical value "1" is found.
The scanning patterns include:
• Top → Scan image from top to bottom
• Bottom → Scan image from bottom to top
• Left → Scan image from left to right
• Right → Scan image from right to left
clc;
clear all;
Image = rgb2gray(imread('https://upload-icon.s3.us-east-2.amazonaws.com/uploads/icons/png/1606078271536061993-512.png'));
BW = imbinarize(Image);
BW = imfill(BW,'holes');
BW = bwareaopen(BW, 100);
BW = padarray(BW,60,60,'both');
BW = imcomplement(BW);
[Image_Height,Image_Width] = size(BW);
%Top (scanning from top to bottom)%
for Row_Scanner = 1: +1: Image_Height
for Column_Scanner = 1: +1: Image_Width
Pixel_Value = BW(Row_Scanner,Column_Scanner);
if(Pixel_Value == 1)
Top = [Row_Scanner Column_Scanner];
break;
end
end
end
%Bottom (scanning from bottom to top)%
for Row_Scanner = Image_Height: -1: 1
for Column_Scanner = 1: +1: Image_Width
Pixel_Value = BW(Row_Scanner,Column_Scanner);
if(Pixel_Value == 1)
Bottom = [Row_Scanner Column_Scanner];
break;
end
end
end
%Left (scanning from left to right)%
for Column_Scanner = 1: +1: Image_Width
for Row_Scanner = 1: +1: Image_Height
Pixel_Value = BW(Row_Scanner,Column_Scanner);
if(Pixel_Value == 1)
Left = [Row_Scanner Column_Scanner];
break;
end
end
end
%Right (scanning from right to left)%
for Column_Scanner = Image_Width: -1: 1
for Row_Scanner = 1: +1: Image_Height
Pixel_Value = BW(Row_Scanner,Column_Scanner);
if(Pixel_Value == 1)
Right = [Row_Scanner Column_Scanner];
break;
end
end
end
Coordinates_Image = zeros(Image_Height,Image_Width,3);
Coordinates_Image(Top(1,1),Top(1,2),1) = 255;
Coordinates_Image(Bottom(1,1),Bottom(1,2),1) = 255;
Coordinates_Image(Left(1,1),Left(1,2),1) = 255;
Coordinates_Image(Right(1,1),Right(1,2),1) = 255;
Top_X = Top(1,2);
Top_Y = Top(1,1);
Bottom_X = Bottom(1,2);
Bottom_Y = Bottom(1,1);
Left_X = Left(1,2);
Left_Y = Left(1,1);
Right_X = Right(1,2);
Right_Y = Right(1,1);
fprintf("Top coordinate is (x,y) -> (%d,%d)\n",Top_X,Top_Y);
fprintf("Bottom coordinate is (x,y) -> (%d,%d)\n",Bottom_X,Bottom_Y);
fprintf("Left coordinate is (x,y) -> (%d,%d)\n",Left_X,Left_Y);
fprintf("Right coordinate is (x,y) -> (%d,%d)\n",Right_X,Right_Y);
subplot(1,2,1); imshow(BW);
title('Image');
subplot(1,2,2); imshow(Coordinates_Image);
title('Coordinate Plot');
xlabel('X-Axis'); ylabel('Y-Axis');

Answer 2

You can do it using a loop. Find the first/last rows and columns whose sum is non-zero and break the loop once the condition is met.
BW = imcomplement(BW);
[r,c] = size(BW);
% Top cordinate: Find first row with non-zero sum
for i=1:r
top = i;
if sum(BW(i,:))~= 0
break
end
end
% Bottom cordinate: Find last row with non zero sum
for i=r:-1:1
bottom = i;
if sum(BW(i,:))~= 0
break
end
end
% Left cordinate: Find first column with non zero sum
for i=1:c
left = i;
if sum(BW(:,i))~= 0
break
end
end
% Right cordinate: find last column with non-zero sum
for i=c:-1:1
right = i;
if sum(BW(:,i))~= 0
break
end
end