How to get HDC of StdPicture object?

[Val]

Hi,

I have StdPicture object in my VB program. How can I get its HDC to work
with it using API?

Thanks,

Val

[Matthew Curland]

In windows, a bitmap can only be selected into one DC at a time. In general,
the bitmap is only selected in when it is drawn to, but there are
occasionally cases where it remains selected. The question of getting the
HDC from the StdPicture object then is actually a little misguided because
you have two objects: the picture, and the device context. The two objects
visit each other, but they are not married. In general, you will pass an hdc
to the StdPicture object, not obtain one from it. You can get an hDC from a
Form, UserControl, PictureBox, etc.

If you're doing a lot of work with a StdPicture, you might want to use the
IPicture interface (obtained through a Set statement) instead of Picture to
operate on it. To see this interface in IntelliSense, make sure you have
'OLE Automation' referenced in your project and 'Show Hidden Members'
checked in the Object Browser context member'. For example, Render through
IPicture actually works, but Render through Picture doesn't. Render is also
a hassle because it uses HiMetric scale, which is a little awkward (the
DrawItem sample in my book uses Render if you have that around and need a
sample). There is also some MSDN explanation of my first paragraph for the
IPicture methods (SelectPicture, CurDC, etc).

-Matt

>
> Hi,
>
> I have StdPicture object in my VB program. How can I get its HDC to work
> with it using API?
>
> Thanks,
>
> Val

[Matthew Curland]

In windows, a bitmap can only be selected into one DC at a time. In general,
the bitmap is only selected in when it is drawn to, but there are
occasionally cases where it remains selected. The question of getting the
HDC from the StdPicture object then is actually a little misguided because
you have two objects: the picture, and the device context. The two objects
visit each other, but they are not married. In general, you will pass an hdc
to the StdPicture object, not obtain one from it. You can get an hDC from a
Form, UserControl, PictureBox, etc.

If you're doing a lot of work with a StdPicture, you might want to use the
IPicture interface (obtained through a Set statement) instead of Picture to
operate on it. To see this interface in IntelliSense, make sure you have
'OLE Automation' referenced in your project and 'Show Hidden Members'
checked in the Object Browser context member'. For example, Render through
IPicture actually works, but Render through Picture doesn't. Render is also
a hassle because it uses HiMetric scale, which is a little awkward (the
DrawItem sample in my book uses Render if you have that around and need a
sample). There is also some MSDN explanation of my first paragraph for the
IPicture methods (SelectPicture, CurDC, etc).

-Matt

>
> Hi,
>
> I have StdPicture object in my VB program. How can I get its HDC to work
> with it using API?
>
> Thanks,
>
> Val

[Karl E. Peterson]

Hi Val --

> I have StdPicture object in my VB program. How can I get its HDC to work
> with it using API?

Like Matt said, you don't. There are, nonetheless, lots of times when it'd be nice
to! See the MemoryDC.zip and CustomBlt.zip samples on my site for classes that fake
this capability for you.

Later... Karl
--
http://www.mvps.org/vb

[Karl E. Peterson]

Hi Val --

> I have StdPicture object in my VB program. How can I get its HDC to work
> with it using API?

Like Matt said, you don't. There are, nonetheless, lots of times when it'd be nice
to! See the MemoryDC.zip and CustomBlt.zip samples on my site for classes that fake
this capability for you.

Later... Karl
--
http://www.mvps.org/vb