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Gudni G. Sigurdsson
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 Posted: Sat Oct 29, 2005 11:27 am Post subject: TCanvas::StretchDraw() execution speed |
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Hi.
Thank you Remy Lebeau and Damon Chandler for your comments on my post about
the EOutOfResource exception. Now, I donīt have storage problems any more.
My only complaint now is the execution speed. To display all jpg images in
a certain directory as thumbnails takes 9,90 sec. When I shortcut my call
to StretchDraw:
nBmap->Canvas->StretchDraw(Rect(0,0,nW,nH),jpegimage);
the code runs in 0.13 sec, i.e. 98% of the time is spent inside
StretchDraw(). Programs like Windows Explorer or ACDSee accomplish similar
tasks very quickly. Is there an alternative method for me to use instead of
StretchDraw() ?
Regards,
Gudni
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Hans Galema
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| Posted: Mon Oct 31, 2005 1:33 pm Post subject: Re: TCanvas::StretchDraw() execution speed |
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Gudni G. Sigurdsson wrote:
| Quote: | ... To display all jpg images in
a certain directory as thumbnails takes 9,90 sec.
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How many jpg's in that directory ?
| Quote: | When I shortcut my call
to StretchDraw:
nBmap->Canvas->StretchDraw(Rect(0,0,nW,nH),jpegimage);
the code runs in 0.13 sec, i.e. 98% of the time is spent inside
StretchDraw(). Programs like Windows Explorer or ACDSee accomplish similar
tasks very quickly. Is there an alternative method for me to use instead of
StretchDraw() ?
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Please comment on Wiljo's suggestion using the Scale property of
TJPEGImage.
Hans.
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Darren Dwyer
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| Posted: Thu Nov 03, 2005 3:01 pm Post subject: Re: TCanvas::StretchDraw() execution speed |
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i'm curious, post the code here...
"Alfred" <alf (AT) no (DOT) spam.not.valid.email> wrote
| Quote: |
nBmap->Canvas->StretchDraw(Rect(0,0,nW,nH),jpegimage);
the code runs in 0.13 sec, i.e. 98% of the time is spent inside
StretchDraw().
StretchDraw() is slow i seen some times ago. One more speed problem is the
TImage repaint if you use it and if you repaint it 20/30 times for second.
You can rewrite StretchDraw() to speed up your code. I have one routine I
can give you if you need. If i remember well it is more faster then |
StretchDraw but i am not sure, it is a old code. If you want try just
response here and i will post my code..
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Alfred
Guest
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| Posted: Fri Nov 04, 2005 10:29 am Post subject: Re: TCanvas::StretchDraw() execution speed |
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| Quote: |
nBmap->Canvas->StretchDraw(Rect(0,0,nW,nH),jpegimage);
the code runs in 0.13 sec, i.e. 98% of the time is spent inside
StretchDraw().
|
StretchDraw() is slow i seen some times ago. One more speed problem is the TImage repaint if you use it and if you repaint it 20/30 times for second.
You can rewrite StretchDraw() to speed up your code. I have one routine I can give you if you need. If i remember well it is more faster then StretchDraw but i am not sure, it is a old code. If you want try just response here and i will post my code..
Alfred
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Alfred
Guest
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| Posted: Sat Nov 05, 2005 11:37 am Post subject: Re: TCanvas::StretchDraw() execution speed |
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"Darren Dwyer" <darrend (AT) bcb-tools (DOT) com> wrote:
| Quote: | i'm curious, post the code here...
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This is a old code i wrote but it work  I am now an expert, I am sure someone can speed up it and make it perfect , better than i can do.
I used TBitmap for the original image and anoter one TBitmap for the background, so after i have created it a simple BitBlt and i can draw it on canvas.
I dont like moltiplication/division in the main code, usually they are slow (on slow machine). I like to make my offset so each time i need a lot of calculation, i can calculate it with a simple "+".
Hope this can help you. Any suggestion/comment will be appreciate, so I can learn more...
Graphics::TBitmap *Picture = new Graphics::TBitmap();
Graphics::TBitmap *Background = new Graphics::TBitmap();
void Stretch(int X, int Y, int Width, int Height, Graphics::TBitmap *Picture)
{
RECT XYScreen={0,0,600,600};
// check if the picture is into the screen, at least one part of the picture
if (X > XYScreen.right || X+Width < XYScreen.left || Y > XYScreen.bottom || Y+Height < XYScreen.top)
return;
float OffsetX,OffsetY;
float ValoreX=0,ValoreY=0;
OffsetX = (float)Picture->Width/Width;
OffsetY = (float)Picture->Height/Height;
int a;
int r=0;
int adda;
// clipping , draw only what you can see into the screen
int Xstart = 0;
int Xend = Width;
if (X < XYScreen.left)
{
Xstart = XYScreen.left - X;
Xend = Width - Xstart;
}
if (X+Width > XYScreen.right)
Xend = Width - ((X+Width)-XYScreen.right);
int Ystart = Y;
int Yend = Y+Height;
if (Y < XYScreen.top)
{
Ystart = XYScreen.top;
ValoreY = (XYScreen.top - Y) * OffsetY;
}
if (Y+Height > XYScreen.bottom)
Yend = (Y+Height) - ((Y+Height)-XYScreen.bottom);
// draw it
int r1,g1,b1;
for (int y=Ystart; y<Yend; y++)
{
BYTE* Src = (BYTE*)Picture->ScanLine[ValoreY];
BYTE* Dest = (BYTE*)Background->ScanLine[y];
ValoreX=(float)Xstart * OffsetX*2;
r=(Xstart+X)*3;
for (int x=Xstart; x
{
adda = int(ValoreX)*3;
r1=Src[adda];
g1=Src[adda+1];
b1=Src[adda+2];
if (r1+g1+b1 != 0) // color = 0 then no draw (transparence)
{
Dest[r]=r1;
Dest[r+1]=g1;
Dest[r+2]=b1;
}
ValoreX += OffsetX;
r+=3;
}
ValoreY += OffsetY;
}
}
Alfred
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