remove background noise(lines) from this image.

I already tried a couple of ways including thresholding, median filter and just to keep red color from the image. But result i am getting is not satisfactory. For example when i used a median filter of [3 3] for image, output image is:

I need to remove remaining noise as well for better recognition of characters. Please help me out.

[Image Analyst]

Why do you want to do this?

[Nishant Sharma]

i am doing security analysis of captchas as my final year project.

[ariki anggi]

you just need to remove only black color. done