No warning to mix screen 0 and screen graphic commands!

[TempodiBasic]

if _SETALPHA works on all the image why does not do this work when we omit a range of color to say all colors into the picture?

Well, you never did that You were doing

_SetAlpha 100, 0

which is equivalent to

_SetAlpha 100, _RGBA32(0, 0, 0, 0)

, a specific color value. If you want to set the alpha for every pixel regardless of color I believe you can omit the second argument all together and do

_SetAlpha 100

. Or alternatively with an image,

_SetAlpha 100, , S2

.

Right! You are right!
using _setalpha transparency%,  , HandleImage&   OR _setalpha transparency%  we get the same result of fading both for background color both for foreground color.

Thank you for more feedback! It appeared me strange that _setalpha did not work on the whole image... there were 2 obstacles
1. _setalpha must be applied just before _putimage
2. the sintax of _setalpha need a comma to distinguish between color and handleimage.