I have a front page with a background image and I want to include a logo that has white background, how to do that without appearing the white background of the logo? I tried includegraphics but it didn't work
The best way heavily depends on the format of the logo image. Examples:
RGB or grayscale bitmap can be opened in GIMP:
If the image mode is not RGB, then convert it to RGB: Image -> Mode -> RGB
Then convert white to transparent (alpha channel): Colors -> Color to Alpha.
Vector image as EPS or PDF: PDF can be uncompressed by PDFtk, e.g.:
pdftk input.pdf cat output output.pdf uncompress
Then, the operation for the white background can be tried to be identified and removed. It requires some knowledge of the format. If it is just a white background that is drawn at the beginning, then it might be not to difficult. Both EPS and PDF have
%as comment character until the end of line. However, the PDF file should be overwritten only, no characters should be inserted or deleted. Otherwise the positions for the cross-reference table gets invalidated.
It can be much more problematic, if the white color is used to overwrite other colored parts.