Added README and other changes

README.md

@@ -0,0 +1,35 @@
+# PSPNG
+
+Sample program to embed messages into PNG images
+
+## Install
+
+Requires zlib, pthread, and sodium header files to compile (These will be distro specific packages)
+
+Build:
+
+```bash
+make
+```
+
+System Wide:
+
+```bash
+make
+make install
+```
+
+## Usage
+
+Embed Message:
+
+pspng --compress -f {input file name} -o {output file name} -m "{input message}"
+
+Extract Message:
+
+pspng --uncompress -f {input file name}
+
+Help Message:
+
+pspng --help
+

cmd/pspng.c

@@ -187,14 +187,17 @@ static void random_window_bit_change(unsigned char *data, unsigned char *raw_dat
 				raw_data[random_num]++;
 			}
 			// Update Current Pixel
-			data[random_num] = raw_data[random_num] - floor((raw_data[random_num-color_range] + raw_data[random_num-((width * color_range) + 1)]) / 2);
+			data[random_num] = raw_data[random_num] - floor((raw_data[random_num-color_range] + 
+						raw_data[random_num-((width * color_range) + 1)]) / 2);
 			// Fixing Next Pixel in Scanline
 			if(!(random_num+color_range > (filter_chunk_byte + (width * color_range) + 1))){
-				data[random_num+color_range] = raw_data[random_num+color_range] - floor((raw_data[random_num] + raw_data[random_num-((width * color_range)+ 1)+color_range]) / 2);
+				data[random_num+color_range] = raw_data[random_num+color_range] - 
+					floor((raw_data[random_num] + raw_data[random_num-((width * color_range)+ 1)+color_range]) / 2);
 			}
 			// Checking Next Scanline type
 			if(data[filter_chunk_byte+((width * color_range) + 1)] == 3){
-				data[random_num+((width * color_range)+1)] = raw_data[random_num+((width * color_range)+1)] - floor((raw_data[random_num+((width * color_range)+1)-color_range] + raw_data[random_num]) / 2);
+				data[random_num+((width * color_range)+1)] = raw_data[random_num+((width * color_range)+1)] - 
+					floor((raw_data[random_num+((width * color_range)+1)-color_range] + raw_data[random_num]) / 2);
 			}
 		} else if(data[filter_chunk_byte] == 4) {
 			// Add Support
@@ -265,9 +268,9 @@ static int crc_embed_data(unsigned char *data, unsigned int data_length, int bit
 	if(offset > 500000) {
 		new_data = calloc(300000, sizeof(unsigned char));
 		for(int k = 0; k < 300000; k++) {
-			new_data[k] = data[offset-(offset-prior_offset)+k];
+			new_data[k] = data[offset-(offset-prior_offset-1)+k];
 		}
-		zlib_compress_data(new_data, 110000, &check_data, &check_data_length);
+		zlib_compress_data(new_data, 100000, &check_data, &check_data_length);
 		match_crc = verify_crc_chunks(check_data, check_data_length, 1, MAX_IDAT_SIZE, message, 1);
 	} else {
 		zlib_compress_data(data, data_length, &check_data, &check_data_length);

src/compress_util.c

@@ -82,6 +82,7 @@ void zlib_compress_data(unsigned char *data_chunk, size_t file_length, unsigned
         unsigned char out[CHUNK];
         int level = 9;
         int method = Z_DEFLATED;
+        //int windowBits = 15;
         int windowBits = 10;
         int memLevel = 9;
         //int strategy = Z_DEFAULT_STRATEGY;