'' examples/manual/gfx/put-alpha-8bit.bas
''
'' Example extracted from the FreeBASIC Manual
'' from topic 'ALPHA'
''
'' See Also: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgAlphaGfx
'' --------

Dim As Any Ptr img8 = 0, img32 = 0
Dim As Integer x, y, i

'' Set up an 8-bit graphics screen
If ScreenRes(320, 200, 8) <> 0 Then
	Print "Could not set the requested graphics mode"
	Sleep
	End 1
End If

For i = 0 To 255
	Palette i,  i, i, i
Next i
Color 255, 0

'' Create an 8-bit image
img8 = ImageCreate(64, 64, 0,  8)

If img8 = 0 Then
	Print "Could not create the 8-bit image"
	Sleep
	End 1
End If

For y = 0 To 63
	For x = 0 To 63
		Dim As Single x2 = x - 31.5
		Dim As Single y2 = y - 31.5
		Dim As Single t = Sqr(x2 ^ 2 + y2 ^ 2) / 5
		PSet img8, (x, y), Sin(t) ^ 2 * 255
	Next x
Next y

Draw String (16, 4), "8-bit Alpha sprite"
Put (16, 16), img8
Sleep


'' Set up a 32-bit graphics screen
If ScreenRes(320, 200, 32) <> 0 Then
	ImageDestroy img8
	Print "Could not set the requested graphics mode"
	Sleep
	End 1
End If

For y = 0 To 199
	For x = 0 To 319
		PSet (x, y), IIf(x - y And 3, RGB(160, 160, 160), RGB(128, 128, 128))
	Next x
Next y

'' Create a 32-bit, fully opaque sprite
img32 = ImageCreate(64, 64, 0, 32)

If img32 = 0 Then
	ImageDestroy img8
	Print "Could not create the 32-bit image"
	Sleep
	End 1
End If

For y = 0 To 63
	For x = 0 To 63
		PSet img32, (x, y), RGB(x * 4, y * 4, 128)
	Next x
Next y

Draw String (16, 4), "Original Alpha channel"
Put (16, 16), img32, Alpha

'' Put a new alpha channel using the 8-bit image
Put img32, (0, 0), img8, Alpha

Draw String (16, 104), "New Alpha channel"
Put (16, 116), img32, Alpha

''Free the memory for the two images
ImageDestroy img8
ImageDestroy img32

Sleep