[SOLVED] Error in Scanline example (from years...)

[jipété]

Hello,

In the last /usr/share/lazarus/3.4.0/examples/scanline, one can read, lines 22-23 of unit1.pas :

Code: Pascal  [Select][+][-]

1.     This example demonstrates how to
2.     - create an image with an internal format similar to Delphi''s pf24bit

and then, line 79 :

Code: Pascal  [Select][+][-]

1.   // create an image with a format similar to Delphi''s pf32bit

So, where is the truth ? 24 or 32 ?

Then, lines 115 and 116 :

Code: Pascal  [Select][+][-]

1. // LineStart is pointer to the start of a scanline with the following format:
2. // 4 bytes per pixel. First byte is blue, second green, third is red.

So I ask : what is the format of the missing fourth byte ?

And finally, one can read :

Code: Pascal  [Select][+][-]

1. line 121 : // fill line with [b]gray[/b]
2. line 123 : PByte(LineStart)[i]:=0; // set red, green and blue to 0 (i.e. black)

I'm lost...
(of course, the image is black with a diagonal red line)

[Handoko]

The fourth byte is for alpha value (transparency). If you want to learn more about scanline and pixel format I recommend this demo:
https://forum.lazarus.freepascal.org/index.php/topic,37242.msg488758.html#msg488758

[jipété]

Hello,

Thanks for the link, very interesting.

But regarding the errors in the text at the beginning of /usr/share/lazarus/3.4.0/examples/scanline/unit1.pas, what can I (we) do ?

[Handoko]

You can report it at the bugtrackter:
https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues

[bytebites]

Line 79 says:

Code: Pascal  [Select][+][-]

1.  // create an image with a format similar to Delphi's pf32bit  

[jipété]

Hello,

sorry for the delay but the forum didn't notify me that there was a reply...

Line 79 says:

Code: Pascal  [Select][+][-]

1.  // create an image with a format similar to Delphi's pf32bit  

Yes we know. So what ?

In my first post there are two lines that talk about the same thing but in a different way, and an unanswered question...
beginning_of_post.png

You can report it at the bugtrackter:
https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues

Done : https://gitlab.com/freepascal.org/lazarus/lazarus/-/issues/41003
Thanks for the link.

[jipété]

will be fixed in 3.6.