when applying im2bw function,the result is black and white image.i want to convert black areas to white and white areas to black
I do not know abc of im2bw. But based on my knowledge of digital images, if its an 8 bit bw, image then subtract the image matrix from a matrix of 255s (i.e., (2^8) -1). This will change all white dots to black (value 255 to 0) and black dots to white (0 to 255) and all intermediate gray levels to equivalent grays of opposite kind. That is why they call it negative images i would suppose.