png import issue

hello,

i'm coming back with a problem....importing a background (png format) I'm seeing it correctly....so after importing a bar or something that aren't a box (for example an arrow) I'm seening a black area that is the part of the picture without image!!!

So how can i solve this?



extern char background[],arrlData[];

PNGUPROP imgProp1,imgProp2;
IMGCTX bkg,arrl

s32 ret1,ret2;

bkg = PNGU_SelectImageFromBuffer(background);
arrl = PNGU_SelectImageFromBuffer(arrlData);

ret1 = PNGU_GetImageProperties(bkg, &imgProp1);
ret2 = PNGU_GetImageProperties(arrl, &imgProp2);

/* Draw background 40x40*/
int i,j;
for(i=0;i<16;i++){
for(j=0;j<12;j++){
Video_DrawPng(bkg, imgProp1, i*40, j*40);
}
}
/* Draw arrow 20x20*/
Video_DrawPng(arrl, imgProp2, 20, 145);