Convert bitdepth of png image

How to convert the image with the following information: ColorType: truecolor Format: png bitDepth: 24

to a png grayscale image with bitdepth=8 in matlab ?

Answer 1

[Christiaan]

Dear Sara,

You can use the function imfinfo to get i.e. the bit depth of the image. With the function rgb2gray you can convert your RGB image into a grey image.

An example how to perform a RGB (24 bitDepth) to a grayscale (8 bitDepth) is shown below:

clc;clear all;close all;

[RGB,map_RGB]  = imread('bitdepth_24bpp_580.png');
RGB_info = imfinfo('bitdepth_24bpp_580.png');
RGB_BitDepth_original = RGB_info.BitDepth

Gray= rgb2gray(RGB);
imwrite(Gray,'imagegrey.png');
grey_info = imfinfo('imagegrey.png');
Grey_BitDepth = grey_info.BitDepth

figure(1);
subplot(2,1,1);imshow(RGB,map_RGB);
subplot(2,1,2);imshow(Gray);

The image that I used can be found in the attachment.

Good Luck! Christiaan van Ommeren