How should I set a pixels color?
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Hi, I am trying to write a simple Mandelbrot set Visual C++ program. I assume that I am not handeling the setting the color of a pixel correctly. Here's some of my code ...
... void CMand_View::OnDraw(CDC* pDC) { ... for( int i=0; i<320; i++ ) { for( int j=0; j<200; j++ ) { int c = CMand_View::Mandel_calcColor( i, j ); pDC->SetPixel(i,j, PALETTEINDEX(c)); } } } ... double CManel_View::Mandel_Abs ( double real, double img ) { double rc = real * real + img * img; return sqrt( rc ); } int CMand_View::Mandel_calcColor( int X, int Y ) { int N; // WHILE-loop control variable double XPos, YPos; // The real and imaginary parts of C double RealPart; // The real part of Z double ImagPart; // The imaginary part of Z int AbsZ; // BOOLEAN; double Temp; double width = 320.0; double height = 200.0; N = 0; AbsZ = TRUE; RealPart = 0; ImagPart = 0; XPos = X / width * (XMax - XMin) + XMin; YPos = Y / height * (YMax - YMin) + YMin; while ( (N < Iterations) && (AbsZ == TRUE) ) { N++; Temp = (RealPart*RealPart) - (ImagPart*ImagPart) + XPos; ImagPart = 2.0 * ImagPart * RealPart + YPos; RealPart = Temp; AbsZ = (( CMand_View::Mandel_Abs (ImagPart, RealPart) <= Bailout) ? TRUE : FALSE); } //end while if (AbsZ == 0 ) { return (N + sColor) % Colors; } else { return 0; } } //end calcColorI think that this ...pDC->SetPixel(i,j, PALETTEINDEX(c));... is not right. :confused:Are you using 256 colours ? Try it in a higher res. The last paremeter as an RGB value ( as returned by the RGB macro ) will work. It will be slow though. A DIBSection would give you a pixel array to set directly instead. Christian No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002
C# will attract all comers, where VB is for IT Journalists and managers - Michael P Butler 05-12-2002
Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002 -
Hi, I am trying to write a simple Mandelbrot set Visual C++ program. I assume that I am not handeling the setting the color of a pixel correctly. Here's some of my code ...
... void CMand_View::OnDraw(CDC* pDC) { ... for( int i=0; i<320; i++ ) { for( int j=0; j<200; j++ ) { int c = CMand_View::Mandel_calcColor( i, j ); pDC->SetPixel(i,j, PALETTEINDEX(c)); } } } ... double CManel_View::Mandel_Abs ( double real, double img ) { double rc = real * real + img * img; return sqrt( rc ); } int CMand_View::Mandel_calcColor( int X, int Y ) { int N; // WHILE-loop control variable double XPos, YPos; // The real and imaginary parts of C double RealPart; // The real part of Z double ImagPart; // The imaginary part of Z int AbsZ; // BOOLEAN; double Temp; double width = 320.0; double height = 200.0; N = 0; AbsZ = TRUE; RealPart = 0; ImagPart = 0; XPos = X / width * (XMax - XMin) + XMin; YPos = Y / height * (YMax - YMin) + YMin; while ( (N < Iterations) && (AbsZ == TRUE) ) { N++; Temp = (RealPart*RealPart) - (ImagPart*ImagPart) + XPos; ImagPart = 2.0 * ImagPart * RealPart + YPos; RealPart = Temp; AbsZ = (( CMand_View::Mandel_Abs (ImagPart, RealPart) <= Bailout) ? TRUE : FALSE); } //end while if (AbsZ == 0 ) { return (N + sColor) % Colors; } else { return 0; } } //end calcColorI think that this ...pDC->SetPixel(i,j, PALETTEINDEX(c));... is not right. :confused: -
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That's a good question! How do I use a palette? I thought just using the marco ...
PALETTEINDEX(c));... would handle all that for me :laugh: Something is going on as my program shows the mandelbrot set all in green! :wtf:the simplest way is to just come up with an array of COLORREF values: COLORREF pal[MAXITERATIONS]; pal[0] = RGB(0,0,0); pal[1] = RGB(64,64,0); pal[2] = RGB(128,128,0); ...etc then, in your loop, just use "pal[c]" instead of that PALETTEINDEX macro. an 8-bit display is pretty rare these days. you might as well just aim for 24-bit color. -c
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Are you using 256 colours ? Try it in a higher res. The last paremeter as an RGB value ( as returned by the RGB macro ) will work. It will be slow though. A DIBSection would give you a pixel array to set directly instead. Christian No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002
C# will attract all comers, where VB is for IT Journalists and managers - Michael P Butler 05-12-2002
Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002Hi Christian, Yes I want to use 256 colors. How could I use the RGB macro when
int CMand_View::Mandel_calcColor( int X, int Y )returns an int and not 3 ints? Should I some how derieve the 3 ints (r, g, b) from c? Where c = CMand_View::Mandel_calcColor( X, Y ); :) -
the simplest way is to just come up with an array of COLORREF values: COLORREF pal[MAXITERATIONS]; pal[0] = RGB(0,0,0); pal[1] = RGB(64,64,0); pal[2] = RGB(128,128,0); ...etc then, in your loop, just use "pal[c]" instead of that PALETTEINDEX macro. an 8-bit display is pretty rare these days. you might as well just aim for 24-bit color. -c
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How should I set pal[3] through pal[255]? Am I using a 8-bit display? How do I use a 24-bit color?
rbc wrote: How should I set pal[3] through pal[255]? pick a set of colors that looks good. in my opinion: 1. fractals work best when the palette fades between two or three colors and 2. generating the palette is as important as picking the right region to render: http://www.smalleranimals.com/thumbfrax/thumbs/_index.htm[^] rbc wrote: Am I using a 8-bit display? i don't know. rbc wrote: How do I use a 24-bit color? don't do anything. just render the pixels by using their COLORREF values. -c
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rbc wrote: How should I set pal[3] through pal[255]? pick a set of colors that looks good. in my opinion: 1. fractals work best when the palette fades between two or three colors and 2. generating the palette is as important as picking the right region to render: http://www.smalleranimals.com/thumbfrax/thumbs/_index.htm[^] rbc wrote: Am I using a 8-bit display? i don't know. rbc wrote: How do I use a 24-bit color? don't do anything. just render the pixels by using their COLORREF values. -c
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Cool web page. You are obviously no stranger to generating fractals! Yet I am. How would you write a mandelbrot program in Visual C++? :)
rbc wrote: How would you write a mandelbrot program in Visual C++? i would start by doing exactly what you're doing just to get a feel for how things work. then i would add controls to move around (zoom in/out, pan, etc.). then i would add palette creation UI (no idea what i'd do for that). then i'd add a bunch of other fractal types. a tiny mandelbrot program[^]
#include "stdio.h"
main()
{
int b=0,c=0,q=60,_=q;for(float i=-20,o,O=0,l=0,j,p;j=O*O,p=l*l,
(!_--|(j+p>4)?fputc(b?q+(_/3):10,(i+=!b,p=j=O=l=0,c++,stdout)),
_=q:l=2*O*l+i/20,O=j-p+o),b=c%q,c<2400;o=-2+b*.05);
}-c
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Hi Christian, Yes I want to use 256 colors. How could I use the RGB macro when
int CMand_View::Mandel_calcColor( int X, int Y )returns an int and not 3 ints? Should I some how derieve the 3 ints (r, g, b) from c? Where c = CMand_View::Mandel_calcColor( X, Y ); :)It looks like you're header for 24 bit colour and Chris has sorted it all out for you. Good luck !!! Christian No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002
C# will attract all comers, where VB is for IT Journalists and managers - Michael P Butler 05-12-2002
Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002 -
Hi, I am trying to write a simple Mandelbrot set Visual C++ program. I assume that I am not handeling the setting the color of a pixel correctly. Here's some of my code ...
... void CMand_View::OnDraw(CDC* pDC) { ... for( int i=0; i<320; i++ ) { for( int j=0; j<200; j++ ) { int c = CMand_View::Mandel_calcColor( i, j ); pDC->SetPixel(i,j, PALETTEINDEX(c)); } } } ... double CManel_View::Mandel_Abs ( double real, double img ) { double rc = real * real + img * img; return sqrt( rc ); } int CMand_View::Mandel_calcColor( int X, int Y ) { int N; // WHILE-loop control variable double XPos, YPos; // The real and imaginary parts of C double RealPart; // The real part of Z double ImagPart; // The imaginary part of Z int AbsZ; // BOOLEAN; double Temp; double width = 320.0; double height = 200.0; N = 0; AbsZ = TRUE; RealPart = 0; ImagPart = 0; XPos = X / width * (XMax - XMin) + XMin; YPos = Y / height * (YMax - YMin) + YMin; while ( (N < Iterations) && (AbsZ == TRUE) ) { N++; Temp = (RealPart*RealPart) - (ImagPart*ImagPart) + XPos; ImagPart = 2.0 * ImagPart * RealPart + YPos; RealPart = Temp; AbsZ = (( CMand_View::Mandel_Abs (ImagPart, RealPart) <= Bailout) ? TRUE : FALSE); } //end while if (AbsZ == 0 ) { return (N + sColor) % Colors; } else { return 0; } } //end calcColorI think that this ...pDC->SetPixel(i,j, PALETTEINDEX(c));... is not right. :confused: