From: couturie <you@example.com>
Date: Sat, 14 Apr 2018 17:02:42 +0000 (+0200)
Subject: cipher_webp
X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/Cipher_code.git/commitdiff_plain/19670cd4e2f20c066355adfe1de7afcde4b8fcce?hp=f78a79609363b2043b18146d6f1d100a5b8a7052

cipher_webp
---

diff --git a/CipherImg/cipher_webp.cpp b/CipherImg/cipher_webp.cpp
new file mode 100644
index 0000000..8176d8f
--- /dev/null
+++ b/CipherImg/cipher_webp.cpp
@@ -0,0 +1,121 @@
+//g++     cipher_webp.cpp   -o cipher_webp -O3
+
+//usage image.webp seed
+//cipher_webp im1.webp 3213
+
+
+#include <iostream>
+#include <fstream>
+#include <iterator>
+#include <vector>
+
+
+using namespace std;
+
+typedef unsigned char uchar;
+
+uchar modulo(int x,int N){ return (x % N + N) %N; }
+
+void fxor(uchar *buf,int sz, int seed,int enc) {
+   int start,end;
+   /*
+  for(int i=1;i<sz;i++) {
+    if(((uint)buf[i-1])==0xFF && ((uint)buf[i])==0xDA) {
+      cout<<"s "<<i+1<<endl;
+      start=i+16;//not nice
+    }
+    if(((uint)buf[i-1])==0xFF && ((uint)buf[i])==0xD9) {
+      cout<<"e "<<i-2<<endl;
+      end=i-2;
+    }
+  }
+   */
+  start=40;
+  end=sz-5;
+  cout<<"start "<<start<<" end "<<end<<endl;
+
+  srand48(seed);
+
+
+  for(int i=0;i<(end-start)/100;i++) {
+    int p=lrand48()%(end-start)+start;
+    if(p<start || p>=end)
+      cout<<"pb"<<endl;
+    while(buf[p-1]==255 || buf[p]==255 ){
+//      cout<<"PROUT"<<endl;
+      p=lrand48()%(end-start)+start;
+      if(p<start || p>=end)
+	cout<<"pb2"<<endl;
+	}
+    uchar v=lrand48()%255;
+    if(enc) {
+      buf[p]=modulo((int)buf[p]+(int)v,255);
+//      buf[p]+=v;
+
+    }
+    else {
+      buf[p]=modulo((int)buf[p]-(int)v,255);
+//      buf[p]-=v;
+
+    }
+  }
+
+/*  if(enc) {
+    for(int i=start;i<end+1;i++) {
+    if(buf[i]==255)
+      cout<<"ARGH"<<(int)buf[i]<<(int)buf[i+1]<<endl;
+
+    // if(buf[i]==0)
+    //  cout<<"ARGH"<<(int)buf[i-1]<<(int)buf[i]<<endl;
+  
+      }
+      }*/
+}
+
+
+int  main(int argc, char **argv){
+  cout<<argv[1]<< endl;
+
+  FILE *fp;
+  fp = fopen(argv[1], "r");
+  fseek(fp, 0L, SEEK_END);
+  int sz = ftell(fp);
+  fseek(fp, 0, SEEK_SET);
+
+  uchar *buf=(uchar*)malloc(sz);
+  uchar *buf2=(uchar*)malloc(sz);
+  fread(buf, sz, 1, fp);
+  fclose(fp);
+
+   
+  int seed=atoi(argv[2]);
+  cout<<sz<<endl;
+ 
+
+  fxor(buf,sz,seed,1);
+  
+
+  fp = fopen("lena2.webp", "w");
+  fwrite (buf , 1, sz, fp);
+  fclose(fp);
+
+  for(int i=0;i<sz;i++) {
+    buf2[i]=buf[i];
+  }
+
+  
+
+
+  fxor(buf2,sz,seed,0);
+
+  fp = fopen("lena3.webp", "w");
+  fwrite (buf2 , 1, sz, fp);
+  fclose(fp);
+
+
+
+
+
+
+
+}