Question

我有这个代码有一个Bresenham（）函数绘制一个简单的行，然后当用户点击右键时，bresenham行被保存为bmp图像。但我遇到的问题是我不知道如何计算bmpInfoHeader结构的宽度和高度。我也不知道如何加载图像以便保存它。

#include<windows.h>
#include<stdio.h>
#include<stdlib.h>
#include<stdint.h>
#include<gl/glut.h>

typedef struct
{
    uint32_t Size;
    uint16_t field;
    uint32_t offset;
}bmpFileHeader;

typedef struct
{
    uint32_t headerSize;
    uint32_t width;
    uint32_t hight;
    uint16_t planes;
    uint16_t dcm;
    uint32_t compression;
    uint32_t imageSize;
    uint32_t bmpx;
    uint32_t bmpy;
    uint32_t colors;
    uint32_t impColors;
}bmpInfoHeader;

float a[90000];
int x0=0,y0=0,xf=0,yf=0;
int print=0;
FILE *bmp = NULL;
bmpInfoHeader *infoHeader;
bmpFileHeader *fileHeader;

void init(void);
void putpixel(int x,int y);
void Bresenham(int x0,int y0,int x1,int y1);
void display(void);
void onMotion(int x,int y);
void onMouse(int button, int e, int x, int y);
void Save();
void onPassive(int x,int y);
void createFileHeader(bmpFileHeader *fileHeader);
void createInfoHeader(bmpInfoHeader *infoHeader);

void init(void)
{
   glClearColor(1.0, 1.0, 1.0, 0.0);
   glMatrixMode(GL_PROJECTION);
   gluOrtho2D(0.0, 300.0, 0.0,300.0);
}

void putpixel(int x,int y)
{
    glColor3f(0.0, 0.0,0.0);
    glBegin(GL_POINTS);
    glVertex2i(x,y);
    glEnd();
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    if(print==1)
       glDrawPixels(300,300,GL_RGB,GL_UNSIGNED_BYTE,a);
    Bresenham(x0,y0,xf,yf);
    glFlush();
}

void Bresenham(int x0,int y0,int x1,int y1)
{
    int dx,dy,p,x,y,px = 1,py = 1,twoDy_Dx,twoDy,i;
    glColor3f(0.0,0.0,1.0);
    dx = x1-x0;
    dy = y1-y0;

    if(dx < 0)
       dx = dx*-1;
    if(dy < 0)
       dy = dy*-1;
    if(x1 < x0)
       px = -1;
    if(y1 < y0)
       py = -1;

    x = x0;
    y = y0;
    if( dx > dy )
    {
        putpixel(x,y);
        p = 2 * dy - dx;
        twoDy_Dx = 2 * ( dy - dx );
        twoDy = 2 * dy;
        for( i = 0; i < dx; i++ )
        {
             if( p >= 0 )
             {
                 y += py;
                 p += twoDy_Dx;
             }
             else
                p += twoDy;
             x += px;
             putpixel(x,y);
        }
   }
   else
   {
       putpixel(x,y);
       p = 2*dx - dy;
       twoDy_Dx = 2 * ( dx - dy );
       twoDy = 2*dx;
       for( i = 0; i < dy; i++ )
       {
           if( p >= 0 )
           {
               x += px;
               p += twoDy_Dx;
           }
           else
              p += twoDy;
           y += py;
           putpixel(x,y);
       }
   }
   glFlush();
}


void onMotion(int x,int y)
{
    xf = x;
    yf = 300-y;
    glutPostRedisplay();
}

void onMouse(int button, int e, int x, int y)
{
    if((button == GLUT_LEFT_BUTTON) && (e == GLUT_DOWN))
    {
        print = 1;
        x0 = xf = x;
        y0 = yf = abs(300-y);
    }
    else if((button == GLUT_LEFT_BUTTON) && (e == GLUT_UP))
       print = 0;
    else if((button == GLUT_RIGHT_BUTTON) && (e == GLUT_UP))
    {
        createFileHeader(fileHeader);
        createInfoHeader(infoHeader);
        Save();
    }
}

void onPassive(int x,int y)
{
    glReadPixels(0.0,0.0,300.0,300.0,GL_RGB,GL_UNSIGNED_BYTE,a);
    Bresenham(x0,y0,xf,yf);
}

void createInfoHeader(bmpInfoHeader *infoHeader)
{
    infoHeader = (bmpInfoHeader*)malloc(sizeof(bmpInfoHeader));

    infoHeader->headerSize = sizeof(bmpInfoHeader);
    infoHeader->width = ???;
    infoHeader->hight = ???;
    infoHeader->planes = 1;
    infoHeader->dcm = 24;
    infoHeader->compression = BI_RGB;
    infoHeader->imageSize =;
    infoHeader->bmpx = 0;
    infoHeader->bmpy = 0;
    infoHeader->colors = 0;
    infoHeader->impColors = 0;
}

void createFileHeader(bmpFileHeader *fileHeader)
{
    fileHeader = (bmpFileHeader*)malloc(sizeof(bmpFileHeader));
    fileHeader->Size = 0;
    fileHeader->field = 0;
    fileHeader->offset = sizeof(bmpFileHeader)+sizeof(bmpInfoHeader);
}

void Save()
{
    uint16_t type;
    if((bmp = fopen("practica no. 7.bmp","wt"))!= NULL)
    {
        type = 0x4D42;
        fwrite(&type,sizeof(type),1,bmp);
        fwrite(&fileHeader,sizeof(bmpFileHeader),1,bmp);
        fwrite(&infoHeader,sizeof(bmpInfoHeader),1,bmp);
    }
    else
       printf("No se pudo crear fichero");
}

int main()
{
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);
    glutInitWindowSize(300, 300);
    glutInitWindowPosition(100, 100);
    glutCreateWindow();
    init();
    glutDisplayFunc(display);
    glutMotionFunc(onMotion);
    glutMouseFunc(onMouse);
    glutPassiveMotionFunc(onPassive);
    glutMainLoop();
}

Answer 1

从您的代码中可以看出，图像是 300 x 300。这意味着，如果您保持比例，您的 bmpInfoHeader.width 和 bmpInfoHeader.height 应该是 300。否则，将窗口宽度乘以比例。

您问题的另一部分在 How to use GLUT to render to a file

中有答案

不知道如何保存bmp图像

1 个答案: