Creating BMP Image contex

copthesaint · **Posted:** Sun Mar 31, 2013 6:42 pm

So for fun I am making this image buffer in c++. Im at the point now where I want to take the information I have from my buffer and compile it into a 32 bit (or 24 bit to start) BMP Image then draw it. however I don't know where to start, I already understand bit shifting and my values in the buffer are all 8 bit each. I also don't want to use other people's libraries. Could anyone point me in a good direction? because right now I'm lost in Google, looking at other peoples code. Here is the code for my current project, btw, plz don't cry because I'm drawing every pixel at such a high level, I'm only doing this because I wanna see how I can and I am very aware of graphics languages:

c++:

//ImageBuffer.h
#ifndef _IMAGEBUFFER_H
#define _IMAGEBUFFER_H

#include <new>
#include <iostream>
#include "Point2D.h"
#include "RGBA.h"
using namespace std;

#define PI 3.14159265

class ImageBuffer{
private:
RGBA * buffer;
unsigned __int32 size;
unsigned __int32 width;
unsigned __int32 height;
unsigned __int32 depth;
unsigned __int32 maxColor;
bool alpha;
public:
ImageBuffer(unsigned __int32,unsigned __int32,unsigned __int32, bool);
~ImageBuffer();

RGBA& operator[] (unsigned __int32);
RGBA& operator[] (Point2D);

void SetSize (unsigned __int32,unsigned __int32);
void SetColorDepth(unsigned __int32);
void SetAlpha (bool);

void Clear(RGBA);
void Invert ();
void DrawDot (Point2D,RGBA);
void DrawOval (Point2D,float,float,RGBA);
void DrawArc (Point2D,float,float,float,float,RGBA);

unsigned __int32 Width ();
unsigned __int32 Height ();

};

#endif

c++:

//ImageBuffer.cpp
#include "ImageBuffer.h"
#ifdef _IMAGEBUFFER_H
ImageBuffer::ImageBuffer(unsigned __int32 w,unsigned __int32 h,unsigned __int32 d, bool a)/*: buffer(0), size (-1), width (w), height(h), depth(d),maxColor(1 << d), alpha(a)*/{
buffer = 0;
size = -1;
width = w;
height = h;
depth = d;
maxColor = (1 << d);
alpha = a;
buffer = new (nothrow) RGBA [width * height]; //0 -- (w*h)-1
if (buffer == 0){
cout << "Could not allocate memory" << endl;
cin.ignore();
return;
}
size = width * height;
RGBA *tempAdd = buffer;
for (int i = 0; i < size; i++){
tempAdd->Set(0,0,0,0);
tempAdd++;
}
return;
}

ImageBuffer::~ImageBuffer(){
if (buffer != 0){
delete [] buffer;
buffer = 0;
}
return;
}

RGBA& ImageBuffer::operator[] (unsigned __int32 index){
return buffer [index];
}
RGBA& ImageBuffer::operator[] (Point2D p2D){
return buffer [p2D.ArrGet(width)];
}

void ImageBuffer::SetSize (unsigned __int32 w ,unsigned __int32 h){
if ((w * h != size) || width != w || height != h){
RGBA * tempBuffer = new (nothrow) RGBA [w * h];
if (tempBuffer == 0){
cout << "could not allocate memory" << endl;
cin.ignore();
return;
}
RGBA * tempBufferAdd = tempBuffer;
for (int i = 0; i < (w * h); i++){
tempBufferAdd->Set(0,0,0,0);
tempBufferAdd++;
}

RGBA * bufferAdd = buffer;
for (__int32 x = 1; x <= width; x++){
for (__int32 y = 1; y <= height; y++){
if (x <= w && x > 0 && y <= h && y > 0){
Point2D temp = Point2D((float)x,(float)y);
tempBuffer[temp.ArrGet(w)] = *bufferAdd;
}
bufferAdd++;
}
}
if (buffer != 0){
delete [] buffer;
}
buffer = tempBuffer;
}
width = w;
height = h;
size = width * height;
return;
}
void ImageBuffer::SetColorDepth(unsigned __int32 d){
depth = d;
unsigned __int32 tempMax = maxColor;
maxColor = (1 << d);
if (maxColor != tempMax){
RGBA * tempAdd = buffer;
for (int i = 0; i < size; i++){
tempAdd ->clr[0] = (unsigned __int16)((float)tempAdd->clr[0] * ((float)maxColor / (float)tempMax));
tempAdd ->clr[1] = (unsigned __int16)((float)tempAdd->clr[1] * ((float)maxColor / (float)tempMax));
tempAdd ->clr[2] = (unsigned __int16)((float)tempAdd->clr[2] * ((float)maxColor / (float)tempMax));
tempAdd ->alpha = (unsigned __int16) ((float)tempAdd->alpha * ((float)maxColor / (float)tempMax));
tempAdd++;
}
}
return;
}
void ImageBuffer::SetAlpha (bool a){
alpha = a;
if (!a){
RGBA *tempAdd = buffer;
for (int i = 0; i < size; i++){
tempAdd ->alpha = 0;
tempAdd++;
}
}
return;
}

void ImageBuffer::Clear(RGBA clr){
RGBA * tempAdd = buffer;
for (int i = 0; i < size; i ++){
*tempAdd = clr;
tempAdd++;
}
return;
}
void ImageBuffer::Invert (){
RGBA * tempAdd = buffer;
for (int i = 0; i < size; i++){
tempAdd->Set ((maxColor-1) - tempAdd->clr[0],(maxColor-1) - tempAdd->clr[1],(maxColor-1) - tempAdd->clr[2],tempAdd->alpha);
tempAdd++;
}
return;
}
void ImageBuffer::DrawDot (Point2D p2D,RGBA clr){
if (p2D.xPos < width && p2D.xPos > 0 && p2D.yPos < height && p2D.yPos > 0){
buffer[p2D.ArrGet(width)] = clr;
}
return;
}
void ImageBuffer::DrawOval (Point2D p2D,float radiusX,float radiusY,RGBA clr){
float perimeter = PI * (float) (radiusX * radiusY);
float angleInc = 360 / perimeter;
for (int i = 0; i < perimeter; i++){
DrawDot (Point2D(p2D.xPos + (radiusX * cos (((angleInc * (float) i)* PI) / 180) ), p2D.yPos + (radiusY * sin (((angleInc * (float) i)* PI) / 180) )),clr);
}
return;
}
void ImageBuffer::DrawArc (Point2D p2D,float radiusX,float radiusY,float initAngle,float finalAngle,RGBA clr){
float perimeter =((finalAngle - initAngle) / 360) * PI * (float) (radiusX * radiusY);
float angleInc = (finalAngle - initAngle) / perimeter;
for (int i = 0; i < perimeter; i++){
DrawDot (Point2D(p2D.xPos + (radiusX * cos (((initAngle + angleInc * (float) i) * PI) / 180) ), p2D.yPos + (radiusY * sin (((initAngle + angleInc * (float) i)*PI)/180) )),clr);
}
return;
}

unsigned __int32 ImageBuffer::Width (){
return width;
}
unsigned __int32 ImageBuffer::Height (){
return height;
}

#endif

Raknarg · **Posted:** Sun Mar 31, 2013 7:01 pm

put of curiosity, why do you name your variables with double underscores?

copthesaint · **Posted:** Sun Mar 31, 2013 7:31 pm

[url]http://msdn.microsoft.com/en-us/library/s3f49ktz(v=vs.80).aspx[/url]
Those are the data types, above is a complete list of c++ data types.

Raknarg · **Posted:** Sun Mar 31, 2013 7:46 pm

Oh I wasn't reading those lines properly -.-' Thanks

copthesaint · **Posted:** Sun Mar 31, 2013 9:42 pm

np, I don't know what the real reason is that the data types have two underscores as well. One wasn't good enough I guess.

TerranceN · **Posted:** Tue Apr 02, 2013 5:50 pm

You need to figure out how to output binary, then you have to follow the BMP specification. In fact, I made a simple (24bit) BMP reader in Turing as an example.

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