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TBitmap from HBITMAP not resizing

 
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André Ávila
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PostPosted: Mon Nov 14, 2005 2:31 pm    Post subject: TBitmap from HBITMAP not resizing Reply with quote


Hello,

I'm a newbie regarding graphics programming, so I'm bit lost here. I'm
trying to write a simple zoom function, so I followed some suggestions I
read here at the group. For some reason, it doesn't work.

I have a TPictureBox inside a TScrollBox. I then get a HBITMAP and set it to
the Handle property of a TBitmap:

Graphics::TBitmap *m_Bmp = new Graphics::TBitmap;

void __fastcall TForm1::LoadImageButtonClick(TObject *Sender) {
HBITMAP hbmp = getImageAsHBITMAP(); // This is legacy code I must use

if (hbmp != NULL) {
m_Bmp->Handle = hbmp;
PaintBox1->SetBounds(0, 0, m_Bmp->Width, m_Bmp->Height);
}

// Reposition ScrollBox1...
}

In the Zoom button, I simply change the Height and Width of the TBitmap:

void __fastcall TForm1::ZoomInButtonClick(TObject *Sender)
{
m_Bmp->Height = m_Bmp->Height * 1.2;
m_Bmp->Width = m_Bmp->Width * 1.2;
PaintBox1->SetBounds(0, 0, m_Bmp->Width, m_Bmp->Height);

// Reposition ScrollBox1...
}

void __fastcall TForm1::ZoomOutButtonClick(TObject *Sender)
{
m_Bmp->Height = m_Bmp->Height * 0.8;
m_Bmp->Width = m_Bmp->Width * 0.8;
PaintBox1->SetBounds(0, 0, m_Bmp->Width, m_Bmp->Height);

// Reposition ScrollBox1...
}

I wrote the OnPaint method for the TPaintBox using BitBlt:

void __fastcall TForm1::PaintBox1Paint(TObject *Sender)
{
BitBlt(PaintBox1->Canvas->Handle, 0, 0,
PaintBox1->Width, PaintBox1->Height,
m_Bmp->Canvas->Handle, 0, 0,
SRCCOPY);
}

As fas as I know, PaintBox1->SetBounds calls OnPaint, because the LoadImage
works fine. However zoom in and zoom out don't work.

Any ideas on what am I doing wrong?


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André Ávila
Guest
PostPosted: Mon Nov 14, 2005 2:33 pm    Post subject: Re: TBitmap from HBITMAP not resizing Reply with quote


Quote:
I have a TPictureBox inside a TScrollBox. I then get a HBITMAP and set it
to
the Handle property of a TBitmap:

Sorry, I meant a TPaintBox inside a TScrollBox.



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Jonathan Benedicto
Guest
PostPosted: Mon Nov 14, 2005 2:44 pm    Post subject: Re: TBitmap from HBITMAP not resizing Reply with quote


André Ávila wrote:
Quote:
In the Zoom button, I simply change the Height and Width of the
TBitmap:

That doesn't work because TBitmap doesn't automatically resize the original
image.

I'd do this:
void __fastcall TForm1::ZoomInButtonClick(TObject *Sender)
{
int PaintBoxWidth = PaintBox1->Width;
int PaintBoxHeight = PaintBox1->Height;

PaintBox1->SetBounds( 0, 0, ( (double)PaintBoxWidth * 1.2 ), (
(double)PaintBoxHeight * 1.2 ) );
// Reposition ScrollBox1...
}

void __fastcall TForm1::ZoomOutButtonClick(TObject *Sender)
{
int PaintBoxWidth = PaintBox1->Width;
int PaintBoxHeight = PaintBox1->Height;

PaintBox1->SetBounds( 0, 0, ( (double)PaintBoxWidth * 0.8 ), (
(double)PaintBoxHeight * 0.8 ) );
// Reposition ScrollBox1...
}

void __fastcall TForm1::PaintBox1Paint(TObject *Sender)
{
PaintBox1->Canvas->StretchDraw( PaintBox1->ClientRect, m_Bmp );
}

HTH

Jonathan



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André Ávila
Guest
PostPosted: Mon Nov 14, 2005 6:37 pm    Post subject: Re: TBitmap from HBITMAP not resizing Reply with quote
Thank you very much, Jonathan. It now works perfectly.


"Jonathan Benedicto" <incorrect (AT) no (DOT) server> escreveu na mensagem
news:4378a29b (AT) newsgroups (DOT) borland.com...
Quote:
André Ávila wrote:
In the Zoom button, I simply change the Height and Width of the
TBitmap:

That doesn't work because TBitmap doesn't automatically resize the
original
image.

I'd do this:
void __fastcall TForm1::ZoomInButtonClick(TObject *Sender)
{
int PaintBoxWidth = PaintBox1->Width;
int PaintBoxHeight = PaintBox1->Height;

PaintBox1->SetBounds( 0, 0, ( (double)PaintBoxWidth * 1.2 ), (
(double)PaintBoxHeight * 1.2 ) );
// Reposition ScrollBox1...
}

void __fastcall TForm1::ZoomOutButtonClick(TObject *Sender)
{
int PaintBoxWidth = PaintBox1->Width;
int PaintBoxHeight = PaintBox1->Height;

PaintBox1->SetBounds( 0, 0, ( (double)PaintBoxWidth * 0.8 ), (
(double)PaintBoxHeight * 0.8 ) );
// Reposition ScrollBox1...
}

void __fastcall TForm1::PaintBox1Paint(TObject *Sender)
{
PaintBox1->Canvas->StretchDraw( PaintBox1->ClientRect, m_Bmp );
}

HTH

Jonathan





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