How to make psp display transparent?

[picobsd]

my display mode is 8888, So a pixel's size in this mode is four bytes, the highest order byte is alpha byte, and I try to set this byte to zero to make current display transparent , but it doesn't work ,why? (I wrote Vram 0x44000000 directly)

[ufoz]

the alpha channel is ignored in the framebuffer. If you need transparency, use a texture and turn on blending.

[picobsd]

the alpha channel is ignored in the framebuffer. If you need transparency, use a texture and turn on blending.

oh, must I use sceGuxxxx ?
I know little about that, my program use pg, a primitive graphic interface wrote by me, it access Vram directly.

[ufoz]

Well, if you want to write to the framebuffer directly like that, you'll have to do the alpha calculations yourself, ie. interpolate between the pixel color and your background color when copying over the image...