Creating a subset of a Bitmap

[Peter Oliphant]

I want to create a new Bitmap which is a portion of an existing Bitmap. For
example, if I have a Bitmap that is 100x100 in size I might want to create a
new Bitmap that is equivalent to the one located at (x,y)=(10,20)
(upper-left hand corner) and is 50x50 in size of the source Bitmap. A
sub-Bitmap if you will, sort of the equivalent to sub-strings for a source
string.

I don't think this works, but something like:

Bitmap^ src_bm = gcnew Bitmap( "bm100x100.bmp" ) ;
Bitmap^ sub_bm = gcnew Bitmap( src_bm(Rectangle(10,20,50,50)) ) ;

Now I can do this via SLOW code ala creating the sub-bitmap of the proper
size and then copying pixels one-by-one from the source bitmap via GetPixel
and SetPixel. But I'm hoping that the construct for a sub-bitmap exists, as
it is quite natural. I can easily DRAW a sub-bitmap with the Graphics class,
but I want to create it as a new Bitmap.

Should I use the pixel-by-pixel method, or is there a faster and/or easier
way?

Thanx in advance for response!

[==Peter==]

PS - I'm developing in MS VC++ 2005 Express ala /cli (managed) code. This is
the Bitmap class I'm speaking of (since there may be more than one with the
same name but different namespaces):

ms-help://MS.VSExpressCC.v80/MS.NETFramework.v20.en/cpref8/html/T_System_Drawing_Image_Members.htm

[Sheng Jiang[MVP]]

1 create an empby bitmap
2 use Graphics::FromImage to create a Graphics from the empby bitmap
3 draw the desired potion of your bitmap to the Graphics
4 save the bitmap you created at step 1 and altered in step 3
--
Sheng Jiang
Microsoft MVP in VC++
"Peter Oliphant" <po*******@roundtripllc.comwrote in message
news:OE**************@TK2MSFTNGP03.phx.gbl...

I want to create a new Bitmap which is a portion of an existing Bitmap.

For

example, if I have a Bitmap that is 100x100 in size I might want to create

a

new Bitmap that is equivalent to the one located at (x,y)=(10,20)
(upper-left hand corner) and is 50x50 in size of the source Bitmap. A
sub-Bitmap if you will, sort of the equivalent to sub-strings for a source
string.

I don't think this works, but something like:

Bitmap^ src_bm = gcnew Bitmap( "bm100x100.bmp" ) ;
Bitmap^ sub_bm = gcnew Bitmap( src_bm(Rectangle(10,20,50,50)) ) ;

Now I can do this via SLOW code ala creating the sub-bitmap of the proper
size and then copying pixels one-by-one from the source bitmap via

GetPixel

and SetPixel. But I'm hoping that the construct for a sub-bitmap exists,

as

it is quite natural. I can easily DRAW a sub-bitmap with the Graphics

class,

but I want to create it as a new Bitmap.

Should I use the pixel-by-pixel method, or is there a faster and/or easier
way?

Thanx in advance for response!

[==Peter==]

PS - I'm developing in MS VC++ 2005 Express ala /cli (managed) code. This

is

the Bitmap class I'm speaking of (since there may be more than one with

the

same name but different namespaces):

ms-help://MS.VSExpressCC.v80/MS.NETFramework.v20.en/cpref8/html/T_System_Dra
wing_Image_Members.htm

>

[Peter Oliphant]

Thanks, Sheng! I tried it and it works great!

Not only that, this opens up a lot more possibilities I hadn't considered,
since I didn't know before how to get a Graphics object from an Image
before! Thanks again!

[==Peter==]

"Sheng Jiang[MVP]" <sh*********@hotmail.com.discusswrote in message
news:eO**************@TK2MSFTNGP05.phx.gbl...

>1 create an empby bitmap
2 use Graphics::FromImage to create a Graphics from the empby bitmap
3 draw the desired potion of your bitmap to the Graphics
4 save the bitmap you created at step 1 and altered in step 3
--
Sheng Jiang
Microsoft MVP in VC++
"Peter Oliphant" <po*******@roundtripllc.comwrote in message
news:OE**************@TK2MSFTNGP03.phx.gbl...

>I want to create a new Bitmap which is a portion of an existing Bitmap.

For

>example, if I have a Bitmap that is 100x100 in size I might want to
create

a

>new Bitmap that is equivalent to the one located at (x,y)=(10,20)
(upper-left hand corner) and is 50x50 in size of the source Bitmap. A
sub-Bitmap if you will, sort of the equivalent to sub-strings for a
source
string.

I don't think this works, but something like:

Bitmap^ src_bm = gcnew Bitmap( "bm100x100.bmp" ) ;
Bitmap^ sub_bm = gcnew Bitmap( src_bm(Rectangle(10,20,50,50)) ) ;

Now I can do this via SLOW code ala creating the sub-bitmap of the proper
size and then copying pixels one-by-one from the source bitmap via

GetPixel

>and SetPixel. But I'm hoping that the construct for a sub-bitmap exists,

as

>it is quite natural. I can easily DRAW a sub-bitmap with the Graphics

class,

>but I want to create it as a new Bitmap.

Should I use the pixel-by-pixel method, or is there a faster and/or
easier
way?

Thanx in advance for response!

[==Peter==]

PS - I'm developing in MS VC++ 2005 Express ala /cli (managed) code. This

is

>the Bitmap class I'm speaking of (since there may be more than one with

the

>same name but different namespaces):

ms-help://MS.VSExpressCC.v80/MS.NETFramework.v20.en/cpref8/html/T_System_Dra
wing_Image_Members.htm

>>