ImageBrush Bugs?

Hi all

I use imagebrush to fill a rectangle
But I found the image will stretch a little for special size.
<StackPanel Background="Red">
<Rectangle Width="500" Height="300" x:Name="r">
<Rectangle.Fill>
<ImageBrush x:Name="imgBrush" ImageSource="d:\\op.png"

Stretch="None"
Viewport="0,0,27,27" ViewportUnits="Absolute"
AlignmentX="Left" AlignmentY="Top"/>
</Rectangle.Fill>
</Rectangle>
</StackPanel>

What I test is use two different size png file with alpha channel.
One is 216x108, the other one is 248x124.
But I found 248x124 is fine (mean didn't stretch), and the other is
stretch a little.
I use viewport "0,0,27,27" to check if stretch or not.
Is there any ideas for the strange result?

Thanks,

HolaMan

One thing to check is whether one of the .pngs has a different DPI than the
other. You can check this by right-clicking on the file and looking at the
properties dialog, then the summary tab (click the "Advanced>>>" button if
you need to on that tab).

-Adam Smith [MS]

"HolaMan" <reality.chang@gmail.com> wrote in message
news:1144813198.091445.226410@z34g2000cwc.googlegroups.com...
> Hi all
>
> I use imagebrush to fill a rectangle
> But I found the image will stretch a little for special size.
> <StackPanel Background="Red">
> <Rectangle Width="500" Height="300" x:Name="r">
> <Rectangle.Fill>
> <ImageBrush x:Name="imgBrush" ImageSource="d:\\op.png"
>
> Stretch="None"
> Viewport="0,0,27,27" ViewportUnits="Absolute"
> AlignmentX="Left" AlignmentY="Top"/>
> </Rectangle.Fill>
> </Rectangle>
> </StackPanel>
>
> What I test is use two different size png file with alpha channel.
> One is 216x108, the other one is 248x124.
> But I found 248x124 is fine (mean didn't stretch), and the other is
> stretch a little.
> I use viewport "0,0,27,27" to check if stretch or not.
> Is there any ideas for the strange result?
>
> Thanks,
>
> HolaMan
>

Thanks for you reply
I have checked the pngs and you are right.
They have different DPI value, one is 72 and the other is 96.

:which DPI will result the right size of ImageBrush? seems 96
Thank you.

> which DPI will result in the right size of ImageBrush

Well, that's sort of a trick question - both DPIs can result in the
"correct" size. If, however, you always want the size WPF
reports/measures/etc to be the same as the pixel dimensions, then yes, 96
DPI will produce that mapping. When you look at the Width or Height of a
Bitmap in Avalon, this value is the width (or height) in pixels of the
Bitmap divided by the DPI * 96, because all of WPF's units are 96'ths of an
inch. This is why a bitmap with 96DPI measures at its pixel dimensions,
because the mapping is identity.

Note that a 72x72 pixel bitmap at 72 DPI is really 1 inch by 1 inch and a
96x96 pixel bitmap at 96 DPI is *also* 1 inch by 1 inch, which is why they
will measure the same in WPF even though they have different pixel
dimensions.

-Adam Smith [MS]


"HolaMan" <reality.chang@gmail.com> wrote in message
news:1145263146.871828.266720@e56g2000cwe.googlegroups.com...
> Thanks for you reply
> I have checked the pngs and you are right.
> They have different DPI value, one is 72 and the other is 96.
>
> :which DPI will result the right size of ImageBrush? seems 96
> Thank you.
>