how to reduce bits per pixel in an image?

If my image in the format of png.. i need to compress this image..so image bit per pixel will be reduced? how this is possible

Answer 1

[Nitin]

Check the imresize function in Matlab

Answer 2

[Image Analyst]

Using imwrite to create a PNG image does the compression for you. Why do you think you need to do anything additional?

[Anusha]

after writing the png format. now i want to apply this image to png codec, again it compressed or not?

if writing the gif image to png format.. how much it will be reduced size.

[Image Analyst]

What GIF image? Images only have a format once they're saved onto disk. Once they're in MATLAB, they're simply an array of numbers. If you use imread() it uncompressed them. They're no longer compressed - it's the full, original array again. The only way to get the compressed data out is if you use fread() but if you did that it's not in a displayable form.