Ok, I have just started AGS, and I was having trouble with GUIs and sprites and the spirtes transparant pixels. I am using 16-bit color.
Is there a way to make it so there is no transparant pixel in a sprite?
Draw your sprite with a solid, 1 pixel line of the transparent colour (i.e. any colour not used in the sprite) down the left side, then when you import it just select the bit you want. Alternatively, use 'Grab whole image', and then right-click the sprite in Sprite Manager, and select 'Crop sprite edges'.
This probably isn't the official way but I usually use the 'Palette Index 0' option for transparency then 'grab entire image' and if you are in 16-bit with a texture with no pallete then then there are no transparent pixels. Work for me.