fonctionnalites mineures

include/extract.h

@@ -10,4 +10,8 @@
 
 void extract(string picture_path, string output_path);
 
+void clean(string picture_path, string output_path);
+
+void get_info(byte *lsb, u32 *length, string picture_path);
+
 #endif //LSD_EXTRACT_H

src/extract.c

@@ -45,5 +45,66 @@ void extract(string picture_path, string output_path) {
     }
 
     EXIT_ON_TRUE(fclose(fp), SYSTEM_CALL_FAIL);
+    free(image);
+}
+
+void clean(string picture_path, string output_path) {
+
+    picture image = 0;
+    u32 width, height;
+
+    EXIT_ON_TRUE(lodepng_decode32_file(&image, &width, &height, picture_path), LODEPNG_ERROR);
+
+    u32 pixels_nb = width * height;         // nombre de pixels
+    u32 lsb = image[0] & 7u;                // nombre de bits occupes par channnel
+    byte mask = ((byte) (0xffu << lsb)) & 0xff;
+
+    image[0] &= ~7u;
+
+    for (u32 i = 1; (i < pixels_nb * 4); i++) {
+        if (i % 4 == 3) continue;   // on skip le canal alpha
+        image[i] &= mask;
+    }
+
+    EXIT_ON_TRUE(lodepng_encode32_file(output_path, image, width, height), LODEPNG_ERROR);
+    free(image);
+}
+
+void get_info(byte *lsb, u32 *length, string picture_path) {
+    picture image = 0;
+    u32 width, height;
+
+    EXIT_ON_TRUE(lodepng_decode32_file(&image, &width, &height, picture_path), LODEPNG_ERROR);
+
+    u32 pixels_nb = width * height;         // nombre de pixels
+    *lsb = image[0] & 7u;                // nombre de bits occupes par channnel
+    u32 real_length = 0;                    // reelle longueur des donnees a lire
+    u32 read_bytes = 0;                     // nombre d'octets lus
+
+    byte data = 0;                          // buffer de lecture d'un octet
+    byte mask = (byte) (1 << (*lsb - 1));    // masque permettant de lire le plus haut bit dissimule
+    byte current_mask;                      // contient les decalages a droite du masque
+    byte buffer_fill = 0;                   // remplissage du buffer
+
+    for (u32 i = 1; (i < pixels_nb * 4) && read_bytes < EMBEDDED_HEADER_SIZE; i++) {
+        if (i % 4 == 3) continue;   // on skip le canal alpha
+        u32 j;
+        for (j = 0, current_mask = mask; j < *lsb; ++j, current_mask >>= 1) {
+            data = (data << 1) | (image[i] & current_mask) >> (*lsb - (j + 1));  // on ajoute le bit courant au buffer
+            if (++buffer_fill == 8) {   // si on a recupere un octet complet
+                if (read_bytes < LEN_HEADER_SIZE) { // si on est en train de lire le header
+                    real_length = (real_length << 8) | data;
+                    if (read_bytes == 3) {
+                        *length = real_length + EMBEDDED_HEADER_SIZE;
+                        free(image);
+                        return;
+                    }
+                }
+                buffer_fill = 0;
+                read_bytes++;   // dans tous les cas un octet de plus a ete lu
+            }
+        }
+    }
+
     free(image);
 }

src/main.c

@@ -23,11 +23,36 @@ int main(int argc, char *argv[]) {
             extract(argv[2], argv[3]);
             return OK;
         }
+
+        if (!strncmp(argv[1], "-c", 2) && argc >= 4) {
+            clean(argv[2], argv[3]);
+            return OK;
+        }
+
+        if (!strncmp(argv[1], "-i", 2) && argc >= 3) {
+            byte lsb = 0;
+            u32 length = 0;
+            string ext = "BKMG";
+
+            get_info(&lsb, &length, argv[2]);
+
+            u32 human = length;
+
+            while (human > 1000) {
+                human /= 1000;
+                ext++;
+            }
+
+            printf("%d bytes (%d%c) hidden in %d bit%s/channel (%d bits/px)\n", length, human, *ext, lsb,
+                   (lsb > 1) ? "s" : "", lsb * 3);
+
+            return OK;
+        }
     }
 
     printf("lsd - a tool to hide things in PNG pictures\nwritten by astequ\n\nUsage :\n\t- hiding     :"
-           " %s -h <picture.png> <data> <output.png>\n\t- extracting : %s -e <picture.png> <output.data>\n", argv[0],
-           argv[0]);
+           " %s -h <picture.png> <data> <output.png>\n\t- extracting : %s -e <picture.png> <output.data>\n\t- cleaning"
+           "   : %s -c <picture.png> <output.png>\n", argv[0], argv[0], argv[0]);
 
     return COMMON_ERROR;
 }