Another technique to hide a message in wbmp image (1 bit image)

Question

1. i would like to know is there another technique or method that i can do to hide
message in wbmp image format without loosing the quality of the image?
if i use LSB technique, it would loosing the quality of the image because LSB technique is no suitable
for WBMP image but it used widely in BMP,JPEG and other image format because the images are
8bit to 24 bit of color representation.please give me a hint to solve my problem. any technique would
be fine as long it can hide message in wbmp image format.
thank you

Answer 1

You are asking for something impossible. To be able to hide a message in an image without noticeable loss of quality, either the image should contain a lot more information than the message, or you should have a preconception of what's in the image. Usually the latter is not possible, and in the case of bitmap images like wbmp the former is not true. You need at least 32 bits to encode one letter (assuming English alphabet) and that's already 32 pixels. But if the picture is big and the 32 pixels are scattered all around you might not notice the change.
Let's make a thought experiment: suppose we were to store 64 characters (a short line of text) using 32 bits per character, we'd need 32*64 pixels just for this information. Experimenting with a graphics program shows that putting more than 8 random pixels in a block of 64x64 pixels already gets noticeable (depending on image). 32*64/8 = 256, so we'll need 256 of 64x64 pixel blocks to store all the information. So total the image should have at least 256*64*64 pixels. If the image was square sized, the size would have to be at least 1024x1024 pixels to encode one single line of text!
I'm not familiar with the wbmp file format though, maybe there's a way to include a hidden comment header that doesn't affect the graphics area.