This program hides the message in an image by LSB manipulation.

main.c to hide data
extract.c to extract it

The image used here (sunflower.jpg) has dimension of: 1200x837 px, 3 color channels

This image is capable of storing 376,650 characters.

Practically we could use more than just the LSB to store the data, and increase the storage capacity as the difference in images is not visible to normal eye for few more bits manipulation.

hidden_message.png has this text:

Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;

Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,

And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.

I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I—
I took the one less traveled by,
And that has made all the difference.
-Robert Frost