tiff format convert using imwrite

Hi all, I have two files in tiff format. One of them is just a black and white text,and the other one is a colorful image. the black and white can be converted only to a tiff format file using imwrite code whereas the latter can also be converted to a jpg format file using imwrite(the same code) can someone explain the difference between these two tiff files and why the latter one is also convertable to a jpg format?

Answer 1

[Walter Roberson]

The black and white one probably reads in as a logical array. imwrite() can write logical arrays to TIFF but not to JPEG. To write a logical array to JPEG use

ArrayGray = uint8(LogicalArray) .* uint8(255);

and then imwrite ArrayGray.

Note, though, that this would produce a grayscale JPEG image, which is fairly rare (I have only ever seen one that was not just a demonstration that creating them was possible.) Some systems might refuse to recognize grayscale JPEG images. You might need to do the conversion to Gray as I indicated and then use

ArrayRGB = ArrayGray(:,:,[1 1 1]);

and then imwrite ArrayRGB