PureBasic Forums - English

Posted: **Thu Oct 05, 2017 2:22 pm**

Hi,

$FFFFFFFF (-1) as color results in a transparent image instead of a white one.

If OpenWindow(0, 0, 0, 900, 100, "DrawAddBorder", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)
  
  CreateImage(0, 450, 100, 32, RGBA(255,255,255,255)) ; -> transparent
  ImageGadget(0, 0, 0, 0, 0, ImageID(0))
  
  CreateImage(1, 450, 100, 32, RGBA(255,255,255,254)) ; -> white
  ImageGadget(1, 450, 0, 0, 0, ImageID(1))
  
  Repeat
    Event = WaitWindowEvent()
  Until Event = #PB_Event_CloseWindow
EndIf

Win10 x64 with PB 5.61 x86

Bernd

Posted: **Thu Oct 05, 2017 5:16 pm**

Bernd,

you need this
you need to use RGB() color instead of RGBA()

Code: Select all

CreateImage(1, 450, 100, 32, RGB(255,255,254) | #PB_Image_Transparent) ; -> white

Code: Select all

If OpenWindow(0, 0, 0, 800, 200, "DrawAddBorder", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)
	StartDrawing(WindowOutput(0))
		DrawingMode(#PB_2DDrawing_Default)
		Box(0, 0, 1200, 200, $00000000)
	StopDrawing()

;---------------------------------------------------------------------------------------------------
	CreateImage(0, 400, 100, 32, RGB(255, 255, 255) | #PB_Image_Transparent) ; -> transparent
	ImageGadget(0, 0, 0, 0, 0, ImageID(0))

	CreateImage(1, 400, 100, 32, RGB(255, 255, 254) | #PB_Image_Transparent) ; -> white
	ImageGadget(1, 400, 0, 0, 0, ImageID(1))

	CreateImage(2, 400, 100, 32, RGBA(255, 255, 255, 255)) ; -> transparent
	ImageGadget(2, 0, 200, 0, 0, ImageID(1))

	CreateImage(2, 400, 100, 32, RGBA(255, 255, 255, 254)) ; -> white
	ImageGadget(2, 400, 100, 0, 0, ImageID(1))

;---------------------------------------------------------------------------------------------------
	StartDrawing(WindowOutput(0))
		DrawingMode(#PB_2DDrawing_Default)
		DrawText(10, 10, "RGB(255, 255, 255) | #PB_Image_Transparent)", $00FFFFFF, $00000000)
	StopDrawing()

	StartDrawing(WindowOutput(0))
		DrawingMode(#PB_2DDrawing_Default)
		DrawText(410, 10, "RGB(255, 255, 254) | #PB_Image_Transparent)", $00FFFFFF, $00000000)
	StopDrawing()

	StartDrawing(WindowOutput(0))
		DrawingMode(#PB_2DDrawing_Default)
		DrawText(10, 110, "RGBA(255, 255, 255, 255)", $00FFFFFF, $00000000)
	StopDrawing()

	StartDrawing(WindowOutput(0))
		DrawingMode(#PB_2DDrawing_Default)
		DrawText(410, 110, "RGBA(255, 255, 255, 254)", $00FFFFFF, $00000000)
	StopDrawing()

;---------------------------------------------------------------------------------------------------
	Repeat
		Event = WaitWindowEvent()
	Until Event = #PB_Event_CloseWindow

	EndIf

marc,

Posted: **Thu Oct 05, 2017 6:37 pm**

infratec wrote:$FFFFFFFF (-1) as color results in a transparent image instead of a white one.

This is in accordance to the documentation.

[u]Documentation of CreateImage()[/u] wrote:[The background] color can be set to #PB_Image_Transparent to create an image with the alpha channel set to full transparent.

Now guess what the value of #PB_Image_Transparent is ...?

-1

Posted: **Thu Oct 05, 2017 6:55 pm**

Hm...

you are right.

But when I create a 32 bit image it should be natural to use RGBA().
And the last parameter of CreateImage() should be a quad, then -1 is out of the normal range.

Bernd

Posted: **Fri Oct 06, 2017 10:42 am**

infratec wrote:But when I create a 32 bit image it should be natural to use RGBA().
And the last parameter of CreateImage() should be a quad, then -1 is out of the normal range.

I agree.

Interesting enough, when in your above code example I replace

Code: Select all

RGBA(255,255,255,255)

with

Code: Select all

#White   ; (some color constants for all OS added in PB 5.60)

then the result is as expected (tested with PB 5.61 x86 and x64 on Windows).

So the source of the problem seems to be an inconsistency of the RGBA() function.

Posted: **Fri Oct 06, 2017 11:55 am**

@Little John
thats because white is $FFFFFF (16777215).

Little John wrote:So the source of the problem seems to be an inconsistency of the RGBA() function.

no, the source of the problem is that #PB_Image_Transparent clashes with a valid RGBA value:

Code: Select all

Debug Bin(#PB_Image_Transparent, #PB_Long)
Debug Bin(RGBA(255, 255, 255, 255), #PB_Long)

@infratec

infratec wrote:And the last parameter of CreateImage() should be a quad, then -1 is out of the normal range.

changing the BackColor parameter to quad wont be enough. RGBA() returns a signed long, and therefor will still return -1. the #PB_Image_Transparent constant has to be changed to a value larger than +4294967295 or smaller than -2147483648.

c ya,
nco2k

Posted: **Fri Oct 06, 2017 12:48 pm**

nco2k wrote:@Little John
thats because white is $FFFFFF (16777215).

Yes, I know.
And if RGBA(255, 255, 255, 255) would return the same value, then this problem wouldn't exist.

nco2k wrote:#PB_Image_Transparent clashes with a valid RGBA value

I know, I already wrote that in my first post in this thread.

Posted: **Fri Oct 06, 2017 7:24 pm**

There is no value for #PB_Image_Transparent that won't clash with a colorref as long as the flag shares a common parameter with the backcolor. The correct solution is to add a new parameter for transparency that is either true or false. Until that happens confusion will abound in the creation of images and the bug reports will keep on coming.

Posted: **Fri Oct 06, 2017 9:14 pm**

I proposed a simple solution in 2015:
http://www.purebasic.fr/english/viewtop ... =3&t=63339

If the depth parameter is 32, then the color parameter should be interpreted as an RGBA value. (24-bit can just interpret it as RGB.)

Then change the value of #PB_Image_Transparent from $FFFFFFFF (conflicts with opaque white) to $00000000 (same as RGBA(0, 0, 0, 0)).

This eliminates all the confusion... all RGBA values work as expected (no conflicts), and code that passes #PB_Image_Transparent still works as expected (black* image with alpha = 0, as is produced by PB now!)

No quad needed, just a clever value for #PB_Image_Transparent!

* or does #PB_Image_Transparent produce white with alpha = 0 ? It's a quick check... If white, then set #PB_Image_Transparent to RGBA(255, 255, 255, 0)

Posted: **Fri Oct 06, 2017 9:46 pm**

Using clever approaches to merge two parameters into one will always lead to confusion of one kind or another. One more optional parameter isn't going to cause an epidemic of arthritis.

Posted: **Sat Oct 07, 2017 9:33 am**

Strictly speaking, I think this is not a bug. According to the documentation of CreateImage(), the function expects a 24 bit RGB value for the 'BackColor' parameter, not a 32 bit RGBA value. And when we only pass RGB values as 'BackColor' parameter, then we won't encounter this issue!

Passing RGBA values as 'BackColor' parameter is currently no advantage anyway, since according to my tests the Alpha value is simply ignored ... with the one exception of RGBA(255,255,255,255) that we are discussing here. So what we are talking about is a feature request, and that's what kenmo did in 2015. As for this request, I agree with netmaestro: Keep it straight and simple.

Posted: **Sat Oct 07, 2017 12:20 pm**

Little John wrote:As for this request, I agree with netmaestro: Keep it straight and simple.

why shouldnt you be able to pre-define the alpha channel? if you want to keep things straight and simple, then you should be able to set all 32bit in one go. currently you can pre-define the first 24bit, but have to manually define the last 8bit. does that make sense to you?

c ya,
nco2k

Posted: **Mon Oct 09, 2017 12:59 pm**

I agree with nco2k, the simplest solution is to use the Alpha channel in the existing BackColor parameter, not to add another parameter.

You've already specified an RGBA image by the depth parameter, so why mask out the A part of the passed value?

(Plus this gives you an alpha choice of 0-255, instead of just 100% transparent like #PB_Image_Transparent does.)

Posted: **Mon Oct 09, 2017 8:40 pm**

kenmo wrote:the simplest solution is to use the Alpha channel in the existing BackColor parameter, not to add another parameter.

You've already specified an RGBA image by the depth parameter, so why mask out the A part of the passed value?

Yes, I see your point now.

Posted: **Mon Oct 09, 2017 11:01 pm**

This isn't a bug, according to Fred it is a feature request.

http://www.purebasic.fr/english/viewtopic.php?f=3&t=63302&p=471887

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CreateImage() 32bit white bug

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