How to save the RGB image after selecting ROI of the image without affecting the original size?

I am using the iamge 'peppers.png' whose size is [384*512*3]. After selecting the ROI from the image using the following code, I have saved the image as 'I1'. But the size of the new image 'I1' is [745*1072*3]. How to save the new image with size [384*512*3]? Please help.

I= imread('peppers.png');
ROI=roipoly(I); %select a close polygon
myImage=findall(gcf,'type','image');
set(myImage,'AlphaData',ROI);
saveas(gcf,'newImage.png');
I1=imread('newImage.png');
size(I1)

Answer 1

[Image Analyst]

Try this, and note that the sizes are the same:

rgbImage = imread('peppers.png');
ROI = roipoly(rgbImage); % Select a closed polygon
subplot(3, 1, 1);
imshow(rgbImage);
axis('on', 'image');
title('Original Image');

% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedRgbImage = bsxfun(@times, rgbImage, cast(ROI, 'like', rgbImage));
whos maskedRgbImage

% Display the masked image.
subplot(3, 1, 2);
imshow(maskedRgbImage);
axis('on', 'image');
title('Masked Image');

% Save the masked image to disk.
imwrite(maskedRgbImage, 'newImage.png');
I2 = imread('newImage.png');
whos I2
% Display the image read in from disk.
subplot(3, 1, 3);
imshow(I2);
axis('on', 'image');
title('Image read In From Disk');

[manami]

Thank you so much

Answer 2

[Image Analyst]

Use imwrite() instead of saveas().

[manami]

Thank you for your answer, But after using imwrite(), I am getting an error:

Error using imwrite (line 427)

Expected DATA to be one of these types:

numeric, logical

Instead its type was matlab.graphics.primitive.Image.

Answer 3

[sarine_nassima]

hi Image Analyst

the ( recognition rate= (no. of correctly identified images / Total no. of images)*100)

my probleme it's how to calculate the no. of correctly identified images???????