web-dev-qa-db-fra.com

Écriture BMP image en c / c ++ pur sans autres bibliothèques

Dans mon algorithme, j'ai besoin de créer une sortie d'informations. Je dois écrire une matrice booléenne dans un fichier bmp. Il doit s'agir d'une image monocromique, où le pixel est blanc si la matrice sur cet élément est vraie. Le problème principal est l'en-tête bmp et comment l'écrire.

c++cimagegraphicsbmp
37
den bardadym

Sans l'utilisation d'aucune autre bibliothèque, vous pouvez regarder le format de fichier BMP . Je l'ai implémenté dans le passé et cela peut être fait sans trop de travail.

Structures de fichiers bitmap

Chaque fichier bitmap contient un en-tête de fichier bitmap, un en-tête d'informations bitmap, une table de couleurs et un tableau d'octets qui définit les bits bitmap. Le fichier a la forme suivante:

BITMAPFILEHEADER bmfh;
BITMAPINFOHEADER bmih;
RGBQUAD aColors [];
BYTE aBitmapBits [];

... voir le format de fichier pour plus de détails

20
Brian R. Bondy

Voyez si cela fonctionne pour vous ... Dans ce code, j'avais 3 tableaux bidimensionnels, appelés rouge, vert et bleu. Chacun était de taille [largeur] [hauteur], et chaque élément correspondait à un pixel - j'espère que cela a du sens!

FILE *f;
unsigned char *img = NULL;
int filesize = 54 + 3*w*h;  //w is your image width, h is image height, both int

img = (unsigned char *)malloc(3*w*h);
memset(img,0,3*w*h);

for(int i=0; i<w; i++)
{
    for(int j=0; j<h; j++)
    {
        x=i; y=(h-1)-j;
        r = red[i][j]*255;
        g = green[i][j]*255;
        b = blue[i][j]*255;
        if (r > 255) r=255;
        if (g > 255) g=255;
        if (b > 255) b=255;
        img[(x+y*w)*3+2] = (unsigned char)(r);
        img[(x+y*w)*3+1] = (unsigned char)(g);
        img[(x+y*w)*3+0] = (unsigned char)(b);
    }
}

unsigned char bmpfileheader[14] = {'B','M', 0,0,0,0, 0,0, 0,0, 54,0,0,0};
unsigned char bmpinfoheader[40] = {40,0,0,0, 0,0,0,0, 0,0,0,0, 1,0, 24,0};
unsigned char bmppad[3] = {0,0,0};

bmpfileheader[ 2] = (unsigned char)(filesize    );
bmpfileheader[ 3] = (unsigned char)(filesize>> 8);
bmpfileheader[ 4] = (unsigned char)(filesize>>16);
bmpfileheader[ 5] = (unsigned char)(filesize>>24);

bmpinfoheader[ 4] = (unsigned char)(       w    );
bmpinfoheader[ 5] = (unsigned char)(       w>> 8);
bmpinfoheader[ 6] = (unsigned char)(       w>>16);
bmpinfoheader[ 7] = (unsigned char)(       w>>24);
bmpinfoheader[ 8] = (unsigned char)(       h    );
bmpinfoheader[ 9] = (unsigned char)(       h>> 8);
bmpinfoheader[10] = (unsigned char)(       h>>16);
bmpinfoheader[11] = (unsigned char)(       h>>24);

f = fopen("img.bmp","wb");
fwrite(bmpfileheader,1,14,f);
fwrite(bmpinfoheader,1,40,f);
for(int i=0; i<h; i++)
{
    fwrite(img+(w*(h-i-1)*3),3,w,f);
    fwrite(bmppad,1,(4-(w*3)%4)%4,f);
}

free(img);
fclose(f);
49
deusmacabre

c'est le meilleur exemple de bas niveau que je connaisse, écrit par Evercat. copié de https://en.wikipedia.org/wiki/User:Evercat/Buddhabrot.c

void drawbmp (char * filename) {

unsigned int headers[13];
FILE * outfile;
int extrabytes;
int paddedsize;
int x; int y; int n;
int red, green, blue;

extrabytes = 4 - ((WIDTH * 3) % 4);                 // How many bytes of padding to add to each
                                                    // horizontal line - the size of which must
                                                    // be a multiple of 4 bytes.
if (extrabytes == 4)
   extrabytes = 0;

paddedsize = ((WIDTH * 3) + extrabytes) * HEIGHT;

// Headers...
// Note that the "BM" identifier in bytes 0 and 1 is NOT included in these "headers".

headers[0]  = paddedsize + 54;      // bfSize (whole file size)
headers[1]  = 0;                    // bfReserved (both)
headers[2]  = 54;                   // bfOffbits
headers[3]  = 40;                   // biSize
headers[4]  = WIDTH;  // biWidth
headers[5]  = HEIGHT; // biHeight

// Would have biPlanes and biBitCount in position 6, but they're shorts.
// It's easier to write them out separately (see below) than pretend
// they're a single int, especially with endian issues...

headers[7]  = 0;                    // biCompression
headers[8]  = paddedsize;           // biSizeImage
headers[9]  = 0;                    // biXPelsPerMeter
headers[10] = 0;                    // biYPelsPerMeter
headers[11] = 0;                    // biClrUsed
headers[12] = 0;                    // biClrImportant

outfile = fopen(filename, "wb");

//
// Headers begin...
// When printing ints and shorts, we write out 1 character at a time to avoid endian issues.
//

fprintf(outfile, "BM");

for (n = 0; n <= 5; n++)
{
   fprintf(outfile, "%c", headers[n] & 0x000000FF);
   fprintf(outfile, "%c", (headers[n] & 0x0000FF00) >> 8);
   fprintf(outfile, "%c", (headers[n] & 0x00FF0000) >> 16);
   fprintf(outfile, "%c", (headers[n] & (unsigned int) 0xFF000000) >> 24);
}

// These next 4 characters are for the biPlanes and biBitCount fields.

fprintf(outfile, "%c", 1);
fprintf(outfile, "%c", 0);
fprintf(outfile, "%c", 24);
fprintf(outfile, "%c", 0);

for (n = 7; n <= 12; n++)
{
   fprintf(outfile, "%c", headers[n] & 0x000000FF);
   fprintf(outfile, "%c", (headers[n] & 0x0000FF00) >> 8);
   fprintf(outfile, "%c", (headers[n] & 0x00FF0000) >> 16);
   fprintf(outfile, "%c", (headers[n] & (unsigned int) 0xFF000000) >> 24);
}

//
// Headers done, now write the data...
//

for (y = HEIGHT - 1; y >= 0; y--)     // BMP image format is written from bottom to top...
{
   for (x = 0; x <= WIDTH - 1; x++)
   {

      red = reduce(redcount[x][y] + COLOUR_OFFSET) * red_multiplier;
      green = reduce(greencount[x][y] + COLOUR_OFFSET) * green_multiplier;
      blue = reduce(bluecount[x][y] + COLOUR_OFFSET) * blue_multiplier;

      if (red > 255) red = 255; if (red < 0) red = 0;
      if (green > 255) green = 255; if (green < 0) green = 0;
      if (blue > 255) blue = 255; if (blue < 0) blue = 0;

      // Also, it's written in (b,g,r) format...

      fprintf(outfile, "%c", blue);
      fprintf(outfile, "%c", green);
      fprintf(outfile, "%c", red);
   }
   if (extrabytes)      // See above - BMP lines must be of lengths divisible by 4.
   {
      for (n = 1; n <= extrabytes; n++)
      {
         fprintf(outfile, "%c", 0);
      }
   }
}

fclose(outfile);
return;
}


drawbmp(filename);
9
ralf htp

Notez que les lignes sont enregistrées de bas en haut et non l'inverse.

De plus, les lignes de balayage doivent avoir une longueur d'octets de multiples de quatre, vous devez insérer des octets de remplissage à la fin des lignes pour garantir cela.

7
codymanix

Code C propre pour la génération d'images Bitmap (BMP)

Image générée:

bitmap image

Le code n'utilise aucune bibliothèque autre que stdio.h . Ainsi, le code peut être facilement incorporé dans d'autres langages de la famille C, comme C++, C #, Java.

#include <stdio.h>

const int bytesPerPixel = 3; /// red, green, blue
const int fileHeaderSize = 14;
const int infoHeaderSize = 40;

void generateBitmapImage(unsigned char *image, int height, int width, char* imageFileName);
unsigned char* createBitmapFileHeader(int height, int width, int paddingSize);
unsigned char* createBitmapInfoHeader(int height, int width);


int main(){
    int height = 341;
    int width = 753;
    unsigned char image[height][width][bytesPerPixel];
    char* imageFileName = "bitmapImage.bmp";

    int i, j;
    for(i=0; i<height; i++){
        for(j=0; j<width; j++){
            image[i][j][2] = (unsigned char)((double)i/height*255); ///red
            image[i][j][1] = (unsigned char)((double)j/width*255); ///green
            image[i][j][0] = (unsigned char)(((double)i+j)/(height+width)*255); ///blue
        }
    }

    generateBitmapImage((unsigned char *)image, height, width, imageFileName);
    printf("Image generated!!");
}


void generateBitmapImage(unsigned char *image, int height, int width, char* imageFileName){

    unsigned char padding[3] = {0, 0, 0};
    int paddingSize = (4 - (width*bytesPerPixel) % 4) % 4;

    unsigned char* fileHeader = createBitmapFileHeader(height, width, paddingSize);
    unsigned char* infoHeader = createBitmapInfoHeader(height, width);

    FILE* imageFile = fopen(imageFileName, "wb");

    fwrite(fileHeader, 1, fileHeaderSize, imageFile);
    fwrite(infoHeader, 1, infoHeaderSize, imageFile);

    int i;
    for(i=0; i<height; i++){
        fwrite(image+(i*width*bytesPerPixel), bytesPerPixel, width, imageFile);
        fwrite(padding, 1, paddingSize, imageFile);
    }

    fclose(imageFile);
}

unsigned char* createBitmapFileHeader(int height, int width, int paddingSize){
    int fileSize = fileHeaderSize + infoHeaderSize + (bytesPerPixel*width+paddingSize) * height;

    static unsigned char fileHeader[] = {
        0,0, /// signature
        0,0,0,0, /// image file size in bytes
        0,0,0,0, /// reserved
        0,0,0,0, /// start of pixel array
    };

    fileHeader[ 0] = (unsigned char)('B');
    fileHeader[ 1] = (unsigned char)('M');
    fileHeader[ 2] = (unsigned char)(fileSize    );
    fileHeader[ 3] = (unsigned char)(fileSize>> 8);
    fileHeader[ 4] = (unsigned char)(fileSize>>16);
    fileHeader[ 5] = (unsigned char)(fileSize>>24);
    fileHeader[10] = (unsigned char)(fileHeaderSize + infoHeaderSize);

    return fileHeader;
}

unsigned char* createBitmapInfoHeader(int height, int width){
    static unsigned char infoHeader[] = {
        0,0,0,0, /// header size
        0,0,0,0, /// image width
        0,0,0,0, /// image height
        0,0, /// number of color planes
        0,0, /// bits per pixel
        0,0,0,0, /// compression
        0,0,0,0, /// image size
        0,0,0,0, /// horizontal resolution
        0,0,0,0, /// vertical resolution
        0,0,0,0, /// colors in color table
        0,0,0,0, /// important color count
    };

    infoHeader[ 0] = (unsigned char)(infoHeaderSize);
    infoHeader[ 4] = (unsigned char)(width    );
    infoHeader[ 5] = (unsigned char)(width>> 8);
    infoHeader[ 6] = (unsigned char)(width>>16);
    infoHeader[ 7] = (unsigned char)(width>>24);
    infoHeader[ 8] = (unsigned char)(height    );
    infoHeader[ 9] = (unsigned char)(height>> 8);
    infoHeader[10] = (unsigned char)(height>>16);
    infoHeader[11] = (unsigned char)(height>>24);
    infoHeader[12] = (unsigned char)(1);
    infoHeader[14] = (unsigned char)(bytesPerPixel*8);

    return infoHeader;
}
6
Minhas Kamal

Voici une variante C++ du code qui fonctionne pour moi. Remarque J'ai dû changer le calcul de la taille pour tenir compte du remplissage de ligne.

// mimeType = "image/bmp";

unsigned char file[14] = {
    'B','M', // magic
    0,0,0,0, // size in bytes
    0,0, // app data
    0,0, // app data
    40+14,0,0,0 // start of data offset
};
unsigned char info[40] = {
    40,0,0,0, // info hd size
    0,0,0,0, // width
    0,0,0,0, // heigth
    1,0, // number color planes
    24,0, // bits per pixel
    0,0,0,0, // compression is none
    0,0,0,0, // image bits size
    0x13,0x0B,0,0, // horz resoluition in pixel / m
    0x13,0x0B,0,0, // vert resolutions (0x03C3 = 96 dpi, 0x0B13 = 72 dpi)
    0,0,0,0, // #colors in pallete
    0,0,0,0, // #important colors
    };

int w=waterfallWidth;
int h=waterfallHeight;

int padSize  = (4-(w*3)%4)%4;
int sizeData = w*h*3 + h*padSize;
int sizeAll  = sizeData + sizeof(file) + sizeof(info);

file[ 2] = (unsigned char)( sizeAll    );
file[ 3] = (unsigned char)( sizeAll>> 8);
file[ 4] = (unsigned char)( sizeAll>>16);
file[ 5] = (unsigned char)( sizeAll>>24);

info[ 4] = (unsigned char)( w   );
info[ 5] = (unsigned char)( w>> 8);
info[ 6] = (unsigned char)( w>>16);
info[ 7] = (unsigned char)( w>>24);

info[ 8] = (unsigned char)( h    );
info[ 9] = (unsigned char)( h>> 8);
info[10] = (unsigned char)( h>>16);
info[11] = (unsigned char)( h>>24);

info[20] = (unsigned char)( sizeData    );
info[21] = (unsigned char)( sizeData>> 8);
info[22] = (unsigned char)( sizeData>>16);
info[23] = (unsigned char)( sizeData>>24);

stream.write( (char*)file, sizeof(file) );
stream.write( (char*)info, sizeof(info) );

unsigned char pad[3] = {0,0,0};

for ( int y=0; y<h; y++ )
{
    for ( int x=0; x<w; x++ )
    {
        long red = lround( 255.0 * waterfall[x][y] );
        if ( red < 0 ) red=0;
        if ( red > 255 ) red=255;
        long green = red;
        long blue = red;

        unsigned char pixel[3];
        pixel[0] = blue;
        pixel[1] = green;
        pixel[2] = red;

        stream.write( (char*)pixel, 3 );
    }
    stream.write( (char*)pad, padSize );
}
5
Cullen Fluffy Jennings

J'ai édité le code htp de ralf pour qu'il se compile (sur gcc, exécutant ubuntu 16.04 lts). Il s'agissait simplement d'initialiser les variables.

    int w = 100; /* Put here what ever width you want */
    int h = 100; /* Put here what ever height you want */
    int red[w][h]; 
    int green[w][h];
    int blue[w][h];


    FILE *f;
    unsigned char *img = NULL;
    int filesize = 54 + 3*w*h;  //w is your image width, h is image height, both int
    if( img )
            free( img );
    img = (unsigned char *)malloc(3*w*h);
    memset(img,0,sizeof(img));
    int x;
    int y;
    int r;
    int g;
    int b;

    for(int i=0; i<w; i++)
    {
            for(int j=0; j<h; j++)
            {
                    x=i; y=(h-1)-j;
                    r = red[i][j]*255;
                    g = green[i][j]*255;
                    b = blue[i][j]*255;
                    if (r > 255) r=255;
                    if (g > 255) g=255;
                    if (b > 255) b=255;
                    img[(x+y*w)*3+2] = (unsigned char)(r);
                    img[(x+y*w)*3+1] = (unsigned char)(g);
                    img[(x+y*w)*3+0] = (unsigned char)(b);
            }
    }

    unsigned char bmpfileheader[14] = {'B','M', 0,0,0,0, 0,0, 0,0, 54,0,0,0};
    unsigned char bmpinfoheader[40] = {40,0,0,0, 0,0,0,0, 0,0,0,0, 1,0, 24,0};
    unsigned char bmppad[3] = {0,0,0};

    bmpfileheader[ 2] = (unsigned char)(filesize    );
    bmpfileheader[ 3] = (unsigned char)(filesize>> 8);
    bmpfileheader[ 4] = (unsigned char)(filesize>>16);
    bmpfileheader[ 5] = (unsigned char)(filesize>>24);

    bmpinfoheader[ 4] = (unsigned char)(       w    );
    bmpinfoheader[ 5] = (unsigned char)(       w>> 8);
    bmpinfoheader[ 6] = (unsigned char)(       w>>16);
    bmpinfoheader[ 7] = (unsigned char)(       w>>24);
    bmpinfoheader[ 8] = (unsigned char)(       h    );
    bmpinfoheader[ 9] = (unsigned char)(       h>> 8);
    bmpinfoheader[10] = (unsigned char)(       h>>16);
    bmpinfoheader[11] = (unsigned char)(       h>>24);

    f = fopen("img.bmp","wb");
    fwrite(bmpfileheader,1,14,f);
    fwrite(bmpinfoheader,1,40,f);
    for(int i=0; i<h; i++)
    {
            fwrite(img+(w*(h-i-1)*3),3,w,f);
            fwrite(bmppad,1,(4-(w*3)%4)%4,f);
    }
    fclose(f);
3
Ignacio Hermosilla

Si vous obtenez des couleurs étranges, changez au milieu de votre image en utilisant la fonction C++ ci-dessus. Assurez-vous d'ouvrir le flux sortant en mode binaire: imgFile.open(filename, std::ios_base::out | std::ios_base::binary);
Sinon, Windows insère des caractères indésirables au milieu de votre fichier! (me cogner la tête sur cette question depuis des heures)

Voir la question connexe ici: Pourquoi l'ofstream insère-t-il un octet 0x0D avant 0x0A?

1
Hadrien Milano

Je voulais juste partager une version améliorée du code de Minhas Kamal parce que même si cela fonctionnait assez bien pour la plupart des applications, j'avais encore quelques problèmes avec. Deux choses très importantes à retenir:

  1. Le code (au moment de l'écriture) appelle free () sur deux tableaux statiques. Cela entraînera le plantage de votre programme. J'ai donc commenté ces lignes.
  2. NE JAMAIS supposer que la hauteur de vos données de pixels est toujours (Width * BytesPerPixel). Il est préférable de laisser l'utilisateur spécifier la valeur de hauteur. Exemple: lors de la manipulation de ressources dans Direct3D, le RowPitch n'est jamais garanti d'être un multiple pair de la profondeur d'octets utilisée. Cela peut provoquer des erreurs dans vos bitmaps générés (en particulier à des résolutions impaires telles que 1366x768).

Ci-dessous, vous pouvez voir mes révisions de son code:

const int bytesPerPixel = 4; /// red, green, blue
const int fileHeaderSize = 14;
const int infoHeaderSize = 40;

void generateBitmapImage(unsigned char *image, int height, int width, int pitch, const char* imageFileName);
unsigned char* createBitmapFileHeader(int height, int width, int pitch, int paddingSize);
unsigned char* createBitmapInfoHeader(int height, int width);



void generateBitmapImage(unsigned char *image, int height, int width, int pitch, const char* imageFileName) {

    unsigned char padding[3] = { 0, 0, 0 };
    int paddingSize = (4 - (/*width*bytesPerPixel*/ pitch) % 4) % 4;

    unsigned char* fileHeader = createBitmapFileHeader(height, width, pitch, paddingSize);
    unsigned char* infoHeader = createBitmapInfoHeader(height, width);

    FILE* imageFile = fopen(imageFileName, "wb");

    fwrite(fileHeader, 1, fileHeaderSize, imageFile);
    fwrite(infoHeader, 1, infoHeaderSize, imageFile);

    int i;
    for (i = 0; i < height; i++) {
        fwrite(image + (i*pitch /*width*bytesPerPixel*/), bytesPerPixel, width, imageFile);
        fwrite(padding, 1, paddingSize, imageFile);
    }

    fclose(imageFile);
    //free(fileHeader);
    //free(infoHeader);
}

unsigned char* createBitmapFileHeader(int height, int width, int pitch, int paddingSize) {
    int fileSize = fileHeaderSize + infoHeaderSize + (/*bytesPerPixel*width*/pitch + paddingSize) * height;

    static unsigned char fileHeader[] = {
        0,0, /// signature
        0,0,0,0, /// image file size in bytes
        0,0,0,0, /// reserved
        0,0,0,0, /// start of pixel array
    };

    fileHeader[0] = (unsigned char)('B');
    fileHeader[1] = (unsigned char)('M');
    fileHeader[2] = (unsigned char)(fileSize);
    fileHeader[3] = (unsigned char)(fileSize >> 8);
    fileHeader[4] = (unsigned char)(fileSize >> 16);
    fileHeader[5] = (unsigned char)(fileSize >> 24);
    fileHeader[10] = (unsigned char)(fileHeaderSize + infoHeaderSize);

    return fileHeader;
}

unsigned char* createBitmapInfoHeader(int height, int width) {
    static unsigned char infoHeader[] = {
        0,0,0,0, /// header size
        0,0,0,0, /// image width
        0,0,0,0, /// image height
        0,0, /// number of color planes
        0,0, /// bits per pixel
        0,0,0,0, /// compression
        0,0,0,0, /// image size
        0,0,0,0, /// horizontal resolution
        0,0,0,0, /// vertical resolution
        0,0,0,0, /// colors in color table
        0,0,0,0, /// important color count
    };

    infoHeader[0] = (unsigned char)(infoHeaderSize);
    infoHeader[4] = (unsigned char)(width);
    infoHeader[5] = (unsigned char)(width >> 8);
    infoHeader[6] = (unsigned char)(width >> 16);
    infoHeader[7] = (unsigned char)(width >> 24);
    infoHeader[8] = (unsigned char)(height);
    infoHeader[9] = (unsigned char)(height >> 8);
    infoHeader[10] = (unsigned char)(height >> 16);
    infoHeader[11] = (unsigned char)(height >> 24);
    infoHeader[12] = (unsigned char)(1);
    infoHeader[14] = (unsigned char)(bytesPerPixel * 8);

    return infoHeader;
}
0
blueshogun96