C / C++ / MFC

15-Oct-05 17:22

Here is my problem:

I need a way to encode X and Y (can be negative numbers and equals) to return me a N integer number always diferent.

(x=2,y=2) = N
(x=-2,y=2) = different N
(x=0,y=0) = another different N

Understand me? Anyone can help me? Thanks in advanced!

C^hris L^osinger15-Oct-05 18:38

15-Oct-05 18:38

can any two pairs of X and Y ever give the same N ?

ex.: X₁, Y₁ = N₁ and X₂, Y₂ = N₁ ?

if not, my first guess is that you can't do it, using 32 bit integers for X,Y and N. you need 64 bits to represent 32x2 bits of input data if you can't have collisions.

Cleek | Image Toolkits | Thumbnail maker

JoaoPe15-Oct-05 19:24

15-Oct-05 19:24

No N should never be the same, that's the main propose :\

My hope is that we can do it only with 'some math'!

Prakash Nadar15-Oct-05 19:04

Prakash Nadar

15-Oct-05 19:04

Do you want to generate a unique value called N?

-prakash

JoaoPe15-Oct-05 19:22

15-Oct-05 19:22

No, any X and Y should give a unique N

(X=2,Y=2) should return always the same N
(X=1,Y=3) should always return any other N

N can be any integer

begray15-Oct-05 22:24

begray

15-Oct-05 22:24

But there are much more (X,Y) pairs than Ns, so every pair can't have unique N.

JoaoPe16-Oct-05 2:38

16-Oct-05 2:38

Problem is:

1. I have to, in some way, save points (x,y) to a skiplist
2. I've to search for that point in that skiplist and return true if is in it otherwise false.
3. But how can I search for a point that is not a single integer? How can I compare if it's higher or lower to go to next node?

C^hris L^osinger16-Oct-05 3:44

16-Oct-05 3:44

Mal-Functi wrote:
But how can I search for a point that is not a single integer? How can I compare if it's higher or lower to go to next node?

have you tried:

if X1 > X2 then
if Y1 > Y2 then
P1 is > P2

Cleek | Image Toolkits | Thumbnail maker

Bob Stanneveld16-Oct-05 10:46

Bob Stanneveld

16-Oct-05 10:46

Hello,

You can try the following:

std::pair<int, int> PointPair(x,y);
if( PointPair > PPn /* other point pair */ )
{ /* do your trick */ }

Hope this helps Smile | :)

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ThatsAlok16-Oct-05 18:54

ThatsAlok

16-Oct-05 18:54

what about MAKELONG MACRO

DWORD dwEncodeVal=MAKELONG(x,y);

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VC Forum Q&A :- I/ IV

DIBitmap

daojinliu15-Oct-05 15:46

daojinliu

15-Oct-05 15:46

int the function OnDraw();I want to create a DIB bitmap using the array pData,and display it on the screen,but I am not fail to do it;Would please tell me how to correct the codes below.

//the array containing color information
unsigned char* pData=new unsigned char[768*576*3];
int y=0, x=0;
for(;y<576;y++)
for(;x<768;x++)
{
pData[x*3+y*768*3]=0;
pData[x*3+1+y*768*3]=0;
pData[x*3+2+y*768*3]=255;
}
//information header

BITMAPINFOHEADER FrameBmi;
FrameBmi.biSize=sizeof(BITMAPINFOHEADER);
FrameBmi.biPlanes=1;
FrameBmi.biCompression=BI_RGB;
FrameBmi.biClrImportant=0;
FrameBmi.biSizeImage=768*576*3;
FrameBmi.biClrUsed=0;
FrameBmi.biBitCount=24;
FrameBmi.biWidth=768;
FrameBmi.biHeight=576;
FrameBmi.biXPelsPerMeter = 0;
FrameBmi.biYPelsPerMeter =0;
//file header
BITMAPFILEHEADER pf;
pf.bfType=0x4d42; //"BM"
pf.bfSize=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+sizeof(char[768*576]);
pf.bfOffBits=sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
pf.bfReserved1=0;
pf.bfReserved2=0;

//BITMAPINFOHEADER
LPBITMAPINFO lpbmi=(LPBITMAPINFO)GlobalAlloc(GMEM_FIXED,sizeof(BITMAPINFOHEADER));
ASSERT(lpbmi);
lpbmi->bmiHeader.biSize=FrameBmi.biSize;
lpbmi->bmiHeader.biPlanes=FrameBmi.biPlanes;
lpbmi->bmiHeader.biCompression=FrameBmi.biCompression;
lpbmi->bmiHeader.biClrImportant=FrameBmi.biClrImportant;
lpbmi->bmiHeader.biSizeImage=FrameBmi.biSizeImage;
lpbmi->bmiHeader.biClrUsed=FrameBmi.biClrUsed;
lpbmi->bmiHeader.biBitCount=FrameBmi.biBitCount;
lpbmi->bmiHeader.biWidth=FrameBmi.biWidth;
lpbmi->bmiHeader.biHeight=FrameBmi.biHeight;
lpbmi->bmiHeader.biXPelsPerMeter=FrameBmi.biXPelsPerMeter;
lpbmi->bmiHeader.biYPelsPerMeter=FrameBmi.biYPelsPerMeter;
lpbmi->bmiColors=NULL;

//Create DIBitmap
CBitmap *OldBitmap;
HBITMAP bmp =::CreateDIBitmap((HDC)pDC,&FrameBmi,CBM_INIT,pData,lpbmi, DIB_RGB_COLORS);
ASSERT(bmp);
//
CBitmap bitmap;
bitmap.Attach(bmp);
CDC dcComp;
dcComp.CreateCompatibleDC(pDC);
OldBitmap=dcComp.SelectObject(&bitmap);
BITMAP bm;
bitmap.GetObject(sizeof(BITMAP),&bm);

// draw bitmap
pDC->BitBlt(0,0,768,576,&dcComp,0,0,SRCCOPY);
dcComp.SelectObject(OldBitmap);
delete [] pData;
GlobalFree(lpbmi);
delteDC(dcComp);

I LOVE VC

-- modified at 6:43 Sunday 16th October, 2005

C^hris L^osinger15-Oct-05 16:56

15-Oct-05 16:56

daojinliu wrote:
but I am not successful

what happens ??

Cleek | Image Toolkits | Thumbnail maker

daojinliu15-Oct-05 18:24

daojinliu

15-Oct-05 18:24

I got a error that there was a ASSERT error in the line of "CreateDIBitmap()",
I am fail to create a DIB bitmap and display it in the monitor.

I LOVE VC

C^hris L^osinger15-Oct-05 18:45

15-Oct-05 18:45

try calling GetLastError just after CreateDIBitmap

Cleek | Image Toolkits | Thumbnail maker

PJ Arends15-Oct-05 20:54

PJ Arends

15-Oct-05 20:54

pData is too small for the bitmap you are trying to create.

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daojinliu16-Oct-05 0:40

daojinliu

16-Oct-05 0:40

yes,the pData should be pData=new unsigned char[768*576*3],but after above update,I am fail to create the DIB bitmap again,

I LOVE VC