Change pixel to Symbols/Chars - c++

Question

I want to try and make, in C++, a Program that takes an Image and scans pixel by pixel, for relatively Dark pixels it prints a space and for Light Pixels it prints symbols like:
"##$%^!M()-~, etc" that will paint new picture with only symbols.
I am new and I really would appreciate some guidance for how it is I can approach that,
I would like to Surprise my teacher.
Thank you very much in advance.
ok that what i already had:
#include <windows.h>
#include <stdio.h>
BYTE* ConvertBMPToRGBBuffer(BYTE* Buffer, int width, int height)
{
// first make sure the parameters are valid
if ((NULL == Buffer) || (width == 0) || (height == 0))
return NULL;
// find the number of padding bytes
int padding = 0;
int scanlinebytes = width * 3;
while ((scanlinebytes + padding) % 4 != 0) // DWORD = 4 bytes
padding++;
// get the padded scanline width
int psw = scanlinebytes + padding;
// create new buffer
BYTE* newbuf = new BYTE[width*height * 3];
// now we loop trough all bytes of the original buffer,
// swap the R and B bytes and the scanlines
long bufpos = 0;
long newpos = 0;
for (int y = 0; y < height; y++)
for (int x = 0; x < 3 * width; x += 3)
{
newpos = y * 3 * width + x;
bufpos = (height - y - 1) * psw + x;
newbuf[newpos] = Buffer[bufpos + 2];
newbuf[newpos + 1] = Buffer[bufpos + 1];
newbuf[newpos + 2] = Buffer[bufpos];
}
return newbuf;
}
BYTE* LoadBMP(int* width, int* height, long* size, LPCTSTR bmpfile)
{
// declare bitmap structures
BITMAPFILEHEADER bmpheader;
BITMAPINFOHEADER bmpinfo;
// value to be used in ReadFile funcs
DWORD bytesread;
// open file to read from
HANDLE file = CreateFile(bmpfile, GENERIC_READ, FILE_SHARE_READ,
NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL);
if (NULL == file)
return NULL; // coudn't open file
// read file header
if (ReadFile(file, &bmpheader, sizeof (BITMAPFILEHEADER), &bytesread, NULL) == false)
{
CloseHandle(file);
return NULL;
}
//read bitmap info
if (ReadFile(file, &bmpinfo, sizeof (BITMAPINFOHEADER), &bytesread, NULL) == false)
{
CloseHandle(file);
return NULL;
}
// check if file is actually a bmp
if (bmpheader.bfType != 'MB')
{
CloseHandle(file);
return NULL;
}
// get image measurements
*width = bmpinfo.biWidth;
*height = abs(bmpinfo.biHeight);
// check if bmp is uncompressed
if (bmpinfo.biCompression != BI_RGB)
{
CloseHandle(file);
return NULL;
}
// check if we have 24 bit bmp
if (bmpinfo.biBitCount != 24)
{
CloseHandle(file);
return NULL;
}
// create buffer to hold the data
*size = bmpheader.bfSize - bmpheader.bfOffBits;
BYTE* Buffer = new BYTE[*size];
// move file pointer to start of bitmap data
SetFilePointer(file, bmpheader.bfOffBits, NULL, FILE_BEGIN);
// read bmp data
if (ReadFile(file, Buffer, *size, &bytesread, NULL) == false)
{
delete[] Buffer;
CloseHandle(file);
return NULL;
}
// everything successful here: close file and return buffer
CloseHandle(file);
return Buffer;
}
void main()
{
int x, y;
long s, s2;
BYTE* a = LoadBMP(&x, &y, &s, L"20140626_143101.bmp);
BYTE* b = ConvertBMPToRGBBuffer(a, x, y);
// what now??
delete[] a;
delete[] b;
}
after i convert the BMP to RGB Buffer what i can do next?? to check about the buffer if it dark or light pixels

Answer 1

I would like to set you on the correct path, that is, without giving you the entire answer. I have found some references which will take you to what it is you would like to learn.
Firstly, one must decode the image. That is copy the image into a variable in another, readable, format. Writing one of these, especially when knew to C++, is not a good idea. But there are many libraries which do this very thing. I recommend:
http://cimg.sourceforge.net/ and then as brief tutorial: http://www.math.ucla.edu/~wittman/hyper/vick/Cimg_tutorial.pdf and Proceeding That to Edit a Single Pixel: http://cimg.sourceforge.net/reference/group__cimg__loops.html (Look at the: Loops over interior regions and borders section)
This hopefully will point you in the right direction.
P.S. Feel free to ask if you have any more questions.