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Hi,
a Graphics object performs clipping, normally to the borders of the applicable Control.
e.g. if you have a Panel, its OnPaint will provide a Graphics object with the clip region
set to correspond to the Panel's size.
You can reduce the drawable area by:
1. setting a smaller clip region
2. choose a smaller Control
I typically prefer 2, hence I add a Panel that gets the size I want my OnPaint to handle.
you were not very specific, the above assumes a .NET environment, and a rectangle with
horizontal and vertical edges (not a rotated one).
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
modified on Friday, March 7, 2008 5:58 AM
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hey there
Yup, c# .net & visual studio 2008...
it makes sense to use a panel, ill try it
the rectangle isn't rotated, what i need to do is draw a time line, and then have lines across it to represent intervals on that time line. Its a tiny bit more complicated than that but in essence thats what i need.
the reason i want to do it in a separate "box" is so that i can dynamically draw this time line instead of just figuring out the coordinates because at a later stage i might want to move or resize it (its going into a control I'm developing)
thanx so mush for the idea, ill let u know how it went!
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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hey
im done doing the basic drawing of the time line, works like a charm!
just out of curiosity, my step brother(a .Net dev as well) mentioned something about double buffering to "combat" the flicker effect.
i put the panel i drew the time line on docked on a form, when i resize the form i call Invalidate() and everything works great... Accept for the flickering
how would i go about implementing the doubleBuffer?
thanx
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Hi,
flickering is due to the amount of time it takes from erasing the first pixel to repainting
the last one. There is no perfect solution, but there are a lot of things that can help a lot:
1.
make sure not to waste CPU cycles in your paint code.
e.g. try using existing pens, brushes, fonts, whatever rather than creating (and disposing)
new ones all the time.
2.
the Control.DoubleBuffered property (since .NET 2.0) is useful; set it true, and .NET will
do all painting for it in an invisible bitmap then paint that in a flash to the screen.
It is transparant to your code, nothing really needs to be changed.
If only one Panel is flicker-critical, just set the DoubleBuffered property for that Panel;
you can set it for the entire Form, but then a larger area will have to be copied from
bitmap to screen every time.
3.
if that is insufficient, it becomes much more complicated.
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
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once again thanx!
im gona try that now... cuz i am creating brushes and pens and rectangles in the paint method and disposing them at the end of it
ill see how it works after a instantiate them in the class and decide if doubleBuffering is necessary
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Hey guys
Im busy working on a control project, in a nutshell its a clock that i draw using GDI+ (i think)
my problem is this, the DrawWhatEver() doesnt work if i use my own graphics object...
private void UserControl1_Load(object sender, EventArgs e)
{
Graphics graphics = this.CreateGraphics();
drawClock(graphics);
}
but i works when i use the OnPaint's e.graphics object
protected override void OnPaint(PaintEventArgs e)
{
drawClock(e.Graphics);
base.OnPaint(e);
}
What is up with that?
thanx
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Well, I'm not really up on all the C# and .NET crap, but in the underlying OS, all painting takes place during the processing of the WM_PAINT message which results in invoking the OnPaint method. In your UserControl1_Load method, just call something like Invalidate() on the window to get a WM_PAINT message sent so it updates its contents. Basically, you update the state of the data and it gets displayed in the OnPaint method. If you want to keep them in snych, you need to invoke painting when you change the data.
Doing my part to piss off the religious right.
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HarveySaayman wrote: What is up with that?
"The Load event occurs after the control is created, but before the control becomes visible for the first time."
Drawing on an invisible control will be, well, invisible
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/coffee.gif)
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haha, now i get it!
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Hi,
here are my guidelines for painting in general:
there are several steps to draw something so it becomes visible on the screen:
1.
decide upon what object you want to draw; it normally is a Control (e.g. a Panel) or a
Form itself. I prefer to add a Panel to a Form, then draw on the Panel.
2.
create some variables (Rectangle, struct, class, whatever) that hold the parameters of
your drawing. For a rectangle that could be top and left coordinate, and width+height,
or just a Rectangle. etc.
3.
create a Paint handler for that Panel, and do all your drawing in there, using the
Graphics class and your variables.
4.
when you want to change things, modify the variables and call Panel.Invalidate() or
one of its overloads (for selective invalidation).
5.
If you want to animate things, perform the move (step 4) inside the Tick handler
of a Windows.Forms.Timer
BTW: if you need to create some objects (Fonts, Pens, Brushes, ...) either keep them
alive in class members (hence create them only once); or create them inside the Paint
handler and don't forget to call Dispose() on them.
Remark: you very rarely need CreateGraphics; OnPaint offers a Graphics object for free.
Luc Pattyn [Forum Guidelines] [My Articles]
This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.
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Hey there,
thanx allot!
this will defiantly help me with the drawing of things,
im gona try drawing my time line on a panel now...
thanx again
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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HarveySaayman wrote: Graphics graphics = this.CreateGraphics();
I don't understand why so many people use this method. It is *wrong*. What led you to use it ? Is there an MS sample out there that uses it ?
As you've discovered, handling hte paint event is the right way to draw your form. CreateGraphics is good to draw something temporary, like a rubberband. What you draw is lost on the first paint event.
Christian Graus - Microsoft MVP - C++
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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Christian Graus wrote: What led you to use it
exploration, im new to drawing so im "playing" around with what im able to do and getting suggestions from you guys, so that i can use these newly discovered "puzzle pieces" in a real world application.
the idea is to explore the drawing class and better understand how it works so that i can write a better control for my application.
im not using Graphics graphics = this.CreateGraphics(); anymore, ive seen the errors in my way
thanx
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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That's cool - I'm not having a shot at you, just generally curious why so many people seem to 'discover' this way of drawing, if there's some book or sample at the bottom of it.
Christian Graus - Microsoft MVP - C++
"also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
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its cool,
i know ur not having a shot at me, but its not always clear to others that theres actually method to my madness  i do things like this on purpose so that i can learn from it and what others have done in the past
Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS
you.suck = (you.passion != Programming)
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Hai,
I am about to design an Source filter. May i know how to create a source filter which should be able to distinguish whether my transport stream is from an live source(ie from an ASI port) or is from the local disk. Please help me.
Thanks and Regards
Angeline
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A DirectShow source filter? What transport stream?
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Following is the piece of code i am using to render grayscale video onto screen. The pixel values are stored as 'int' in the variable disp_frame whose declaration is given below. 50 pixel buffers of size 176 X 144 is used.
I thought of creating bitmap out of these pixels and then use BitBlt to render it to the screen. But the CreateDIBSection is creating an exception when running in Debug code. It should be some syntax error. Could anyone debug it out.
int p=0,i=0,j=0,q=0;
extern int disp_frame[50][144][176];
///////////////////////
BITMAPINFOHEADER bmi;
BITMAPINFO bm;
RGBQUAD rgbarray[256];
bmi.biSize = sizeof(BITMAPINFOHEADER);
bmi.biWidth = 176;
bmi.biHeight = 144;
bmi.biPlanes = 1;
bmi.biBitCount = 8;
bmi.biCompression = BI_RGB;
bmi.biSizeImage = 0;
bmi.biXPelsPerMeter = 0;
bmi.biYPelsPerMeter = 0;
bmi.biClrUsed = 0;
bmi.biClrImportant = 0;
bm.bmiHeader = bmi;
for (int color_index = 0; color_index < 256; color_index++)
{
rgbarray[color_index].rgbBlue = i;
rgbarray[color_index].rgbGreen = i;
rgbarray[color_index].rgbRed = i;
rgbarray[color_index].rgbReserved = 0;
}
bm.bmiColors[1] = rgbarray[0];
/////////////////////
CRect rcClient;
GetClientRect(rcClient); // See Note 1
rcClient.right=176;
rcClient.bottom=144;
/*****************Doubtful routine starts here*******
HDC hDC;
hDC = CreateDC("DISPLAY",NULL,NULL,NULL);
HDC memDC = CreateCompatibleDC(hDC);
CreateDIBSection(hDC,bitmap,DIB_PAL_COLORS,ppbits,NULL,0);
HBITMAP memBM = CreateCompatibleBitmap(hDC,176,144);
SelectObject(memDC,memBM);
BitBlt(memDC,150,100,176,144,hDC,0,0,SRCCOPY);
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jossion wrote: CreateDIBSection(hDC,bitmap,DIB_PAL_COLORS,ppbits,NULL,0);
What is "bitmap"?
A BITMAPINFO has a BITMAPINFOHADER in it. It also has 1 of the 256 RGBQUAD
structs you need already in it. You need to allocate this all in one contiguous section
of memory.
The initialization of the color table is wrong, unless you want all black.
This line is all wrong and useless - "bm.bmiColors[1] = rgbarray[0];"
You are rendering in the wrong direction, unless you're trying to copy pixels from that DISPLAY dc to a memory dc.
That "DISPLAY" DC ... why not just use the DC for the client area of a window?
You should use DIB_RGB_COLORS when creating the dibsection so the call doesn't overwrite your grayscale color table.
You never use the dibsection you create.
Something like this should help you create the DIBsection....I don't know what you're trying to render so I
can't provide an example for that until you clear that up  ...
BITMAPINFO *bm = (BITMAPINFO *)new BYTE[sizeof(BITMAPINFO) + 255 * sizeof(RGBQUAD)];
bm->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bm->bmiHeader.biWidth = 176;
bm->bmiHeader.biHeight = 144;
bm->bmiHeader.biPlanes = 1;
bm->bmiHeader.biBitCount = 8;
bm->bmiHeader.biCompression = BI_RGB;
bm->bmiHeader.biSizeImage = 0;
bm->bmiHeader.biXPelsPerMeter = 0;
bm->bmiHeader.biYPelsPerMeter = 0;
bm->bmiHeader.biClrUsed = 0;
bm->bmiHeader.biClrImportant = 0;
for (int color_index = 0; color_index < 256; color_index++)
{
bm->bmiColors[color_index].rgbBlue = color_index; <font color="Green">
bm->bmiColors[color_index].rgbGreen = color_index; <font color="Green">
bm->bmiColors[color_index].rgbRed = color_index; <font color="Green">
</font> bm->bmiColors[color_index].rgbReserved = 0;
}
BYTE *pBitmapBits;
HBITMAP hBitmap = ::CreateDIBSection(NULL, bm, DIB_RGB_COLORS, (void**)&pBitmapBits, NULL, 0);
if (hBitmap)
{
<font color="Green">
::DeleteObject(hBitmap);
}
delete[] (BYTE *)bm;
Tell me what you want to do rendering-wise and I'll try to fill in the sample code.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.freetls.fastly.net/script/Forums/Images/coffee.gif)
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I have pixel values of successive frames of video stored in int disp_frame[50][144[176], 50 buffers of size 176X144. Under a timer of 40ms I was doing all the stuff which i posted. Previously I was using setpixel to draw the video. Now for better speed I thought of doing BitBlt. So there came a ncessity to convert the raw pixel values to bitmap. That is what should happen in the rendering section. Creating DC,then Creating DIB then copying to memory DC, then using BitBlt or optional zooming with StretchBlt. I know that there are still excellent ways of doing it. But I thought of learning all techniques by coding it and seeing the performance. So I would like you to fill the rendering area with BitBlt(including routines for DC creation) for displaying pixels in disp_frame.As I have read the pixel values should be copied to (void**)&pBitmapBits. Basically I am not a person with programming background. that's why my code might have irritated you a bit. Anyhow a small apology for my mistakes.
bitmap is of type BITMAPINFO *bitmap.
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I tried to do that.
Here's a breakdown of the rendering problem...
SetPixel is a really bad choice for rendering video, so moving to a bit-block-transfer
implementation is the right direction.
To use BitBlt()/StretchBlt(), you need a source DC with a bitmap containing the pixels
you want to render selected into it.
Since your pixel data comes in raw int format, you need a HBITMAP bitmap that allows you direct access
to its pixel data - thats what a DIBSection is for.
Once you have all that, there's more that can be optimized - You don't have to recreate the DIB section
every time you render a frame. It can be created once, before you start rendering frames.
Same applies to the memory DC - it only needs to be created once and have the DIBSection selected into it.
That means every 40ms, you only need to copy the pixel bits to the DIBSection, get a destination DC
for where you're going to draw, and blt.
Here's an expanded example...
<span style="color: Green;">
extern int disp_frame[50][144][176];
LONG VideoWidth = 176;
LONG VideoHeight = 144;
WORD BitsPerPixel = 8;
LONG BytesPerDIBSectionRow = (((VideoWidth * (long)BitsPerPixel + 31L) & (~31L)) / 8L);
BITMAPINFO *pBMI = 0;
BYTE *pBitmapBits = 0;
HBITMAP hDIBSection = 0;
HGDIOBJ hOldMemBitmap = 0;
HDC memDC = 0;
bool InitVideoRenderer()
{
pBMI = (BITMAPINFO *)new BYTE[sizeof(BITMAPINFO) + 255 * sizeof(RGBQUAD)];
pBMI->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pBMI->bmiHeader.biWidth = VideoWidth;
pBMI->bmiHeader.biHeight = VideoHeight;
pBMI->bmiHeader.biPlanes = 1;
pBMI->bmiHeader.biBitCount = BitsPerPixel;
pBMI->bmiHeader.biCompression = BI_RGB;
pBMI->bmiHeader.biSizeImage = 0;
pBMI->bmiHeader.biXPelsPerMeter = 0;
pBMI->bmiHeader.biYPelsPerMeter = 0;
pBMI->bmiHeader.biClrUsed = 0;
pBMI->bmiHeader.biClrImportant = 0;
for (int color_index = 0; color_index < 256; color_index++)
{
pBMI->bmiColors[color_index].rgbBlue = color_index;
pBMI->bmiColors[color_index].rgbGreen = color_index;
pBMI->bmiColors[color_index].rgbRed = color_index;
pBMI->bmiColors[color_index].rgbReserved = 0;
}
hDIBSection = ::CreateDIBSection(NULL, pBMI, DIB_RGB_COLORS, (void**)&pBitmapBits, NULL, 0);
if (hDIBSection)
{
memDC = ::CreateCompatibleDC(0);
hOldMemBitmap = ::SelectObject(memDC, hDIBSection);
return true;
}
else
{
delete[] (BYTE *)pBMI;
pBMI = 0;
return false;
}
}
void RenderFrame(int FrameIndex, HWND destwnd, int x, int y)
{
<span style="color: Green;">
BYTE *pCurDIBSectionRow = pBitmapBits;
for (int row = 0; row < VideoHeight; row++)
{
for (int col = 0; col < VideoWidth; col++)
{
pCurDIBSectionRow[col] = (BYTE)(disp_frame[FrameIndex][row][col] >> 24); <span style="color: Green;">
}
pCurDIBSectionRow += BytesPerDIBSectionRow;
}
<span style="color: Green;">
HDC ClientDC = ::GetDC(destwnd);
::BitBlt(ClientDC, x, y, pBMI->bmiHeader.biWidth, pBMI->bmiHeader.biHeight, memDC, 0, 0, SRCCOPY);
::ReleaseDC(destwnd, ClientDC);
}
void CleanupVideoRenderer()
{
if (hDIBSection)
{
::SelectObject(memDC, hOldMemBitmap);
hOldMemBitmap = 0;
::DeleteDC(memDC);
memDC = 0;
::DeleteObject(hDIBSection);
hDIBSection = 0;
delete[] (BYTE *)pBMI;
pBMI = 0;
}
}
<span style="color: Green;">
if (InitVideoRenderer())
{
RenderFrame(0, *this, 0, 0); <span style="color: Green;">
CleanupVideoRenderer();
}
*edit* fixed 32bpp source to 8bpp destination pixel data conversion
Last modified: 10hrs 52mins after originally posted --
Mark Salsbery
Microsoft MVP - Visual C++
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thank you very much. This is the first time I am getting a complete solution from Codeproject. cheers.
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No problem!
I just realized I treated your source data as 16bpp when it's 32bpp (int!) LOL I'll change that.
Cheers,
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Hi Salsbery,
For the past one year the piece of code you gave me satisfied my requirements excellently. Now I have come up with a problem of displaying colour video. I will need help once again in modifying the code to colour. The main problem is how I should arrange the pixels and where to write it. What are the BITMAPINFO parameters that I have to change. Hope to get a reply at the earliest.
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jossion wrote: modifying the code to colour
How many bits per pixel?
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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