Creation image JPEG

**Flaherty Mc Coillean** · 11/05/2010, 12h53

Bonjour à tous,

Très mauvais en langage c, j'essaye de créer une image jpg à l'aide de la librairie libjpeg

Je crée un tableau de "nblig" lignes et "nbcol*3" colonnes, pourquoi "nbcol*3" ? Car je range les valeurs de R, de G et de B à la suite on a donc 3 fois plus de colonnes que l'image que l'on souhaite obtenir.
Ensuite j'essaye d'utiliser libjpeg pour configurer et créer mon image jpeg.

Je n'ai aucun problème à compiler, mais lorsque je lance mon programme, j'obtiens l'erreur suivante :

Empty JPEG image (DNL not supported)

voici mon code (attention ça risque de vous piquer les yeux) :

Code :

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#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <jpeglib.h>
 
 
int main(void)
{
unsigned char R[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,};
unsigned char G[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,124,120,116,112,108,104,100,96,92,88,84,80,76,72,68,64,60,56,52,48,44,40,36,32,28,24,20,16,12,8,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,};   
unsigned char B[]={131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,124,120,116,112,108,104,100,96,92,88,84,80,76,72,68,64,60,56,52,48,44,40,36,32,28,24,20,16,12,8,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,};
unsigned char **mat;
int i=0, j=0, nblig=256, nbcol=256;
 
 
mat=malloc(nblig*sizeof(unsigned char*));
if (mat==NULL)
   {
   printf("erreur lors de l'allocation memoire de : mat\n");
   free(mat);
   mat=NULL;
   exit(EXIT_FAILURE);   
   }
else
   {
   for (i=0;i<nblig;i++)
      {
      mat[i]=malloc((nbcol*3)*sizeof(unsigned char*));
      if (mat[i]==NULL)
         {
         printf("erreur lors de l'allocation memoire de : mat[i]\n");
         for (j=0;j<i;j++)
            {
            free(mat[j]);
            mat[j]=NULL;
            }
         free(mat);
         mat=NULL;
         exit(EXIT_FAILURE);         
         }      
      }
   }
 
for (i=0;i<nblig;i++)
   {
   for (j=0;j<(nbcol*3);j=j+3)
      {
      mat[i][j]=R[i];
      mat[i][j+1]=G[i];
      mat[i][j+2]=B[i];
      }
   }
 
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr       jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
 
cinfo.image_width      = nblig;
cinfo.image_height     = nbcol;
cinfo.input_components = 3;
cinfo.in_color_space   = JCS_RGB;
 
FILE * outfile;
outfile = fopen("/home/flaherty/Bureau/hauteur_panache/test.jpeg", "wb");
if (outfile == NULL) {
   printf("can't open /home/flaherty/Bureau/hauteur_panache/test.jpeg\n");
   exit(1);
   }
jpeg_stdio_dest(&cinfo, outfile);
 
 
jpeg_start_compress(&cinfo, TRUE);
 
JSAMPROW row_pointer[1];      /
int row_stride;              
row_stride = nbcol * 3;   
while (cinfo.next_scanline < cinfo.image_height) {
   row_pointer[0] = mat[cinfo.next_scanline * row_stride];
   jpeg_write_scanlines(&cinfo, row_pointer, 1);
   }
 
jpeg_finish_compress(&cinfo);
 
 
}

Une idée sur ce qui coince ?

Invité(e) · 11/05/2010, 14h20

Bonjour,

Lorsqu'on observe le code de libjpeg, on s'apperçoit que cette erreur n'est déclenchée à cette ligne :

Code :

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  /* Sanity check on image dimensions */
  if (cinfo->image_height <= 0 || cinfo->image_width <= 0 || 
      cinfo->num_components <= 0 || cinfo->input_components <= 0)
    ERREXIT(cinfo, JERR_EMPTY_IMAGE);

Un simple

Code :

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jpeg_set_defaults(&cinfo);

peut résoudre ton problème.

A mettre après

Code :

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jpeg_create_compress(&cinfo);

par exemple.

Invité(e) · 11/05/2010, 14h22

Par contre, ta boucle d'écriture pose problème, tu parcourt ta matrice comme si elle était d'un seul tenant, alors que c'est un fait un tableau de tableaux.

Voici la boucle corrigée :

Code :

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    while (cinfo.next_scanline < cinfo.image_height) {
        row_pointer[0] = mat[cinfo.next_scanline];
        jpeg_write_scanlines(&cinfo, row_pointer, 1);
    }

**Flaherty Mc Coillean** · 11/05/2010, 17h16

Merci, mais malheureusement j'ai toujours la même erreur...

Invité(e) · 11/05/2010, 17h32

Envoyé par Flaherty Mc Coillean

Merci, mais malheureusement j'ai toujours la même erreur...

Peux tu poster le code corrigé ?

**Flaherty Mc Coillean** · 11/05/2010, 17h53

le voilà :

Code :

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#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <jpeglib.h>
 
int main(void)
{
unsigned char R[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,};
unsigned char G[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96,100,104,108,112,116,120,124,128,131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,124,120,116,112,108,104,100,96,92,88,84,80,76,72,68,64,60,56,52,48,44,40,36,32,28,24,20,16,12,8,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,};   
unsigned char B[]={131,135,139,143,147,151,155,159,163,167,171,175,179,183,187,191,195,199,203,207,211,215,219,223,227,231,235,239,243,247,251,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,251,247,243,239,235,231,227,223,219,215,211,207,203,199,195,191,187,183,179,175,171,167,163,159,155,151,147,143,139,135,131,128,124,120,116,112,108,104,100,96,92,88,84,80,76,72,68,64,60,56,52,48,44,40,36,32,28,24,20,16,12,8,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,};
unsigned char **mat;
int i=0, j=0, nblig=256, nbcol=256;
 
mat=malloc(nblig*sizeof(unsigned char*));
if (mat==NULL)
   {
   printf("erreur lors de l'allocation memoire de : mat\n");
   free(mat);
   mat=NULL;
   exit(EXIT_FAILURE);   
   }
else
   {
   for (i=0;i<nblig;i++)
      {
      mat[i]=malloc((nbcol*3)*sizeof(unsigned char*));
      if (mat[i]==NULL)
         {
         printf("erreur lors de l'allocation memoire de : mat[i]\n");
         for (j=0;j<i;j++)
            {
            free(mat[j]);
            mat[j]=NULL;
            }
         free(mat);
         mat=NULL;
         exit(EXIT_FAILURE);         
         }      
      }
   }
 
for (i=0;i<nblig;i++)
   {
   for (j=0;j<(nbcol*3);j=j+3)
      {
      mat[i][j]=R[R[i]];
      mat[i][j+1]=G[R[i]];
      mat[i][j+2]=B[R[i]];
      }
   }
 
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr       jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
 
cinfo.image_width      = nblig;
cinfo.image_height     = nbcol;
cinfo.input_components = 3;
cinfo.in_color_space   = JCS_RGB;
 
FILE * outfile;
outfile = fopen("/home/flaherty/Bureau/hauteur_panache/test.jpeg", "wb");
if (outfile == NULL) {
   printf("can't open /home/flaherty/Bureau/hauteur_panache/test.jpeg\n");
   exit(1);
   }
jpeg_stdio_dest(&cinfo, outfile);
 
 
jpeg_start_compress(&cinfo, TRUE);
jpeg_set_defaults(&cinfo);
 
JSAMPROW row_pointer[1];       
int row_stride;             
row_stride = nbcol * 3;   
 
for(i=0;i<nblig;i++)
   {
   row_pointer[0] = mat[i];
   jpeg_write_scanlines(&cinfo, row_pointer, 1);
   }
 
jpeg_finish_compress(&cinfo)
 
}

pour la boucle, j'ai aussi essayé avec :

Code :

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    while (cinfo.next_scanline < cinfo.image_height) {
        row_pointer[0] = mat[cinfo.next_scanline];
        jpeg_write_scanlines(&cinfo, row_pointer, 1);
    }

sans plus de résultats...

Creation image JPEG

C

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