Graphics

Re: OpenGL, DirectX, WPF ??

30-Jun-07 7:16

If you're using SetPageUnit() then maybe this will be of interest:
Types of Coordinate Systems[^]

"Go that way, really fast. If something gets in your way, turn."

Webcam

genna9926-Jun-07 10:42

genna99

26-Jun-07 10:42

Hi to All!
I have a problem to catch event from button on webcam using DirectX or WIA.
Any ideas.

OpenGL, DirectX, WPF ??

BusyDeveloper21-Jun-07 21:55

BusyDeveloper

21-Jun-07 21:55

I am thinking of enhancing the 3D display of the scene in my app. Currently I'm using a simple method with OpenGL.

The idea is displaying a scene with a LOT of objects, but there is no need for complex rendering (I mean: no need for extreme realism). I want to be able to change viewpoint, zoom, etc., but it's not a game, so no need for maximum speed.

What are my options ? OpenGL, DirectX ? Maybe WPF ? Unsure | :~

Things to consider ?

Thanks in advance.

El Corazon26-Jun-07 5:47

El Corazon

26-Jun-07 5:47

BusyDeveloper wrote:
Things to consider ?

if your focus is on the "scene" of objects, not on the objects themselves, you might change focus a bit towards a scene-graph. This is not a replacement of OpenGL or DirectX, it is a higher level operation that is simply an organization construct. Objects are placed on the scene-graph and the scene-graph is then rendered via OpenGL or DirectX. There are many scene-graphs available, but if you are using OpenGL already, OpenSceneGraph might be easiest to switch to.

http://www.openscenegraph.com/index.php[^]

_________________________
Asu no koto o ieba, tenjo de nezumi ga warau.
Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)

Zooming the line in OpenGL

a_david12320-Jun-07 23:19

a_david123

20-Jun-07 23:19

Dear All
Regards!
I am using OpenGL(CSGL) in C#, i draw a line and now want to zoomin and zoomout it in OpenGL, kindly help me while developing program for Zooming in openGL.

Regards
David Sigh | :sigh:

david

How to AddAlpha Values ??

SandipG 20-Jun-07 18:22

20-Jun-07 18:22

How can i change alpha channel values without rinning Height*width loop
Is there any way that i can drawimage without altering alpha values of background??.
i mean i have two images where bye sequences of pixels will be as follows

22 0
34 0
56 0
255 14
55 0
22 0
44 0
255 10
23 0
37 0
56 0
255 14
51 0
28 0
44 0
255 10

now i want to replace 255 with other values or Replace 0's with values from first column.

Mark Salsbery21-Jun-07 6:59

21-Jun-07 6:59

I'm confused. How does a drawimage alter alpha values of a background?

"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder

SandipG 21-Jun-07 18:22

21-Jun-07 18:22

If i create the graphics object from a bitmap object which has some alpha values.
Now using this graphics object if i draw some other bitmap on firstbitmap the alpha values are altered i mean they will be set to 255.

Mark Salsbery22-Jun-07 5:37

22-Jun-07 5:37

Gotcha.

Since there's only two compositing modes, you may have to loop through and combine the alpha
values the way you want to.

SandipG wrote:
now i want to replace 255 with other values or Replace 0's with values from first column.

CompositingModeSourceOver works for the "Replace 0's with values from first column" case but not
for the "replace 255 with other values" case.

Here's some code you can play with to see the compositing results...

// Create a 20x20 ARGB bitmap
Gdiplus::Bitmap Bitmap1(20, 20, PixelFormat32bppARGB);
 
Gdiplus::Rect rect(0, 0, 20, 20);
 
// Create a Graphics object from the bitmap
Gdiplus::Graphics *pBitmapGraphics1 = Gdiplus::Graphics::FromImage(&Bitmap1);
 
// Try different compositing modes
//pBitmapGraphics1->SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
pBitmapGraphics1->SetCompositingMode(Gdiplus::CompositingModeSourceOver);
 
// Try different colors to blend - brush is background, pen is foreground
Gdiplus::SolidBrush solidbrush(Gdiplus::Color(0xFF,0x00,0xFF,0x00));//Gdiplus::Color::Transparent);
Gdiplus::Pen solidpen(Gdiplus::Color(0x40,0xFF,0x00,0x00), 1.0);//Gdiplus::Color::Transparent, 1.0);
 
// Fill the background with the brush color and draw the first row with the pen, using
// the current compositing mode
pBitmapGraphics1->FillRectangle(&solidbrush, rect);
pBitmapGraphics1->DrawLine(&solidpen, 0, 0, 19, 0);
 
// Release the bitmap from the graphics object so we can look at the pixel bits
delete pBitmapGraphics1;
pBitmapGraphics1 = 0;
 
// Look at the pixel bits (look at pRGBQuads in a debugger memory window)
Gdiplus::BitmapData bitmapData;
Bitmap1.LockBits(&rect,	ImageLockModeRead, PixelFormat32bppARGB, &bitmapData);
RGBQUAD *pRGBQuads = (RGBQUAD *)bitmapData.Scan0;
Bitmap1.UnlockBits(&bitmapData); //<code><-- put breakpoint here</code>

"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder

SandipG 24-Jun-07 19:47

Re: How to AddAlpha Values ?? [modified]

24-Jun-07 19:47

I played with it but it works with pens and brushes only.
No change in effect of DrawImage.

Mark Salsbery25-Jun-07 6:28

Image Warp Function needed.

25-Jun-07 6:28

With DrawImage(), on the destination Graphics...

SetCompositingMode(CompositingModeSourceCopy) will cause the drawn image to replace whatever was
in the destination image.

SetCompositingMode(CompositingModeSourceOver) will cause the drawn image to be blended with
whatever was in the destination image (the resulting alpha values are not always set to 255).

You should get the same results as with a pen and a brush. A bitmap filled with values with alpha
set to 0 drawn on an image with alpha set to, say, 0x80, will leave the destination alpha 80.
That matches your replace 0s with the first column alpha value, just like with a brush or pen.

Regardless, I guess my point was that to get the results you want with the alpha channels, I
don't believe the APIs are going to do it.

Even though you were looking to avoid it, LockBits/UnlockBits makes it relatively trivial to loop
through the images and combine them yourself.

Mark

-- modified at 13:09 Monday 25th June, 2007

"Go that way, really fast. If something gets in your way, turn."

SandipG 20-Jun-07 2:02

Re: Image Warp Function needed.

20-Jun-07 2:02

Hi ,
I need a function to warp image .
Warp(HBITMAP,HBITMAP,point1,point2,point3,point4) or
Warp(Byte*,Byte*,inputsize,point1,point2,point3,point4)
this function would tranform image to fit the quadrilateral pointed by four points.
there is artical on codeproject AAform which is really very good but it is very slow.
for me that quadrilateral will always be convex.

Some help in this will be highly appreciated
Thanks in advance.
Sandip.

Force Code20-Jun-07 6:39

Force Code

20-Jun-07 6:39

There's the old PlgBlt fron GDI:

"The PlgBlt function performs a bit-block transfer of the bits of color data from the specified rectangle in the source device context to the specified parallelogram in the destination device context."

However, it probably doesn't do the anti-aliasing mentioned in the AAForm article.

Have you looked at the GDI+ functions? There looks to be about twenty different 'DrawImage' methods in the Graphics class, as well as a SetSmoothingMode method with a SmoothingModeAntiAlias as an option (although this method may just apply to lines and curves).

Re: Image Warp Function needed.

SandipG 20-Jun-07 18:09