Bitmap to PictureBox control problem

[Sharon]

I encountered a strange behavior when doing ‘new Bitmap’:

The following code works fine and the given bitmap file is shown on the
PictureBox (the m_DrawArea) in the correct bitmap sizes:

private Graphics m_gMapImg;
private Bitmap m_backroundImag e;
private Bitmap MapImg;
private PictureBox m_DrawArea;

protected void OnResize(object sender, System.EventArg s e)
{
if( m_MapImg != null )
{
m_MapImg.Dispos e();
m_gMapImg.Dispo se();
}
if( m_DrawArea.Widt h != 0 && m_DrawArea.Heig ht != 0 )
{
m_MapImg = new Bitmap(m_DrawAr ea.Width, m_DrawArea.Heig ht);
m_gMapImg = Graphics.FromIm age(m_MapImg);
}
}

protected override void OnPaint(PaintEv entArgs e)
{
m_gMapImg.Clear (Color.Transpar ent);
m_gMapImg.DrawI mage(m_backroun dImage, 0, 0);

m_DrawArea.Imag e = m_MapImg;

base.OnPaint(e) ;
}

public Bitmap BackImage
{
set {
if( value != null )
m_backroundImag e = new Bitmap(value);
}
}

public string BackgroundImage Path
{
set {
if( System.IO.File. Exists(value) )
BackImage = new Bitmap(value);
}
}
But as you can see, the ‘new Bitmap’ is done twice when the
BackgroundImage Path property is called. And the BackImage property is
creating a new bitmap out of the given bitmap.

So I changed the code of the BackImage to:
public Bitmap BackImage
{
set {
if( value != null )
m_backroundImag e = value;
}
}

And now the bitmap file that is given to me by the BackgroundImage Path
property is shown on the PictureBox (the DrawArea) control as a thumbnail and
not in his original size.

The same problem occurs if only change the BackgroundImage Path property to:
public string BackgroundImage Path
{
set {
if( System.IO.File. Exists(value) )
m_backroundImag e = new Bitmap(value);
}
}

I can’t make sense of it.
Can anybody tell me why or how it acts so strangely?

---------
Thanks
Sharon

[Andrew Kirillov]

Hello,

m_gMapImg.DrawI mage(m_backroun dImage, 0, 0) will draw the specified image,
using its original physical size according to it's DPI and screen
resolution.

Here is a note from MSDN:
"The physical width, measured in inches, of an image is the pixel width
divided by the horizontal resolution. For example, an image with a pixel
width of 216 and a horizontal resolution of 72 dots per inch has a physical
width of 3 inches. Similar remarks apply to pixel height and physical
height."

So, if you want to draw image using it's width and height in pixels, you
can:
m_gMapImg.DrawI mage(m_backroun dImage, 0, 0, m_backroundImag e.Width,
m_backroundImag e.Height)

--
With best regards,
Andrew

http://www.codeproject.com/script/pr...asp?id=1181072
"Sharon" <Sh*****@newsgr oups.nospam> wrote in message
news:39******** *************** ***********@mic rosoft.com...

I encountered a strange behavior when doing 'new Bitmap':

The following code works fine and the given bitmap file is shown on the
PictureBox (the m_DrawArea) in the correct bitmap sizes:

private Graphics m_gMapImg;
private Bitmap m_backroundImag e;
private Bitmap MapImg;
private PictureBox m_DrawArea;

protected void OnResize(object sender, System.EventArg s e)
{
if( m_MapImg != null )
{
m_MapImg.Dispos e();
m_gMapImg.Dispo se();
}
if( m_DrawArea.Widt h != 0 && m_DrawArea.Heig ht != 0 )
{
m_MapImg = new Bitmap(m_DrawAr ea.Width, m_DrawArea.Heig ht);
m_gMapImg = Graphics.FromIm age(m_MapImg);
}
}

protected override void OnPaint(PaintEv entArgs e)
{
m_gMapImg.Clear (Color.Transpar ent);
m_gMapImg.DrawI mage(m_backroun dImage, 0, 0);

m_DrawArea.Imag e = m_MapImg;

base.OnPaint(e) ;
}

public Bitmap BackImage
{
set {
if( value != null )
m_backroundImag e = new Bitmap(value);
}
}

public string BackgroundImage Path
{
set {
if( System.IO.File. Exists(value) )
BackImage = new Bitmap(value);
}
}
But as you can see, the 'new Bitmap' is done twice when the
BackgroundImage Path property is called. And the BackImage property is
creating a new bitmap out of the given bitmap.

So I changed the code of the BackImage to:
public Bitmap BackImage
{
set {
if( value != null )
m_backroundImag e = value;
}
}

And now the bitmap file that is given to me by the BackgroundImage Path
property is shown on the PictureBox (the DrawArea) control as a thumbnail
and
not in his original size.

The same problem occurs if only change the BackgroundImage Path property
to:
public string BackgroundImage Path
{
set {
if( System.IO.File. Exists(value) )
m_backroundImag e = new Bitmap(value);
}
}

I can't make sense of it.
Can anybody tell me why or how it acts so strangely?

---------
Thanks
Sharon

[Sharon]

Surprisingly for me it works as you said.
Thanks a lot
Sharon