Font smoothing using cairo

I am trying to smooth text rendering using anti-aliasing. But it's not anti-aliased.

First line is a png image created using pango and cairo. Second line is just an html <span> tag. It's in firefox, Ubuntu with Gnome DE. The difference can be better understood if you compare "W" and "v" between two lines.

The code responsible to draw text can be found on http://pastie.org/1073683 Font options are set on lines 17 and 20 like so:

// setting up antialiasing
cairo_font_options_set_antialias(cfo, CAIRO_ANTIALIAS_GRAY);

// set the font options to cairo
cairo_set_font_options(this开发者_JAVA百科->cro, cfo);

Could anyone please tell me how can I make those two lines look the same?

cairo_font_options_set_antialias(cfo, CAIRO_ANTIALIAS_GRAY);

You asked for it, you got it. To get a match you'd need CAIRO_ANTIALIAS_SUBPIXEL. This is however not appropriate when you draw text to an image that might be displayed on another machine. There's no guarantee that the monitor on that machine is an LCD panel with the RGB stripes in a predictable order. Or that it in landscape orientation. Or that it is displayed with the exact original size. When there's a mismatch, the text will look quite poor.