diff --git a/backend/2of5.c b/backend/2of5.c
index 94b9dee9..d32c6868 100644
--- a/backend/2of5.c
+++ b/backend/2of5.c
@@ -65,7 +65,7 @@ int matrix_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 	concat (dest, "41111");
 	
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -99,7 +99,7 @@ int industrial_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 	concat (dest, "31113");
 	
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -132,7 +132,7 @@ int iata_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 	concat (dest, "311");
 	
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -166,7 +166,7 @@ int logic_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 	concat (dest, "311");
 	
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -199,7 +199,7 @@ int interleaved_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 
 		length = ustrlen(source);
 
-		strcpy(temp, source);
+		strcpy(temp, (char*)source);
 		source[0] = '0';
 
 		for(i = 0; i <= length; i++)
@@ -234,7 +234,7 @@ int interleaved_two_of_five(struct zint_symbol *symbol, unsigned char source[])
 	concat (dest, "311");
 	
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 
 }
@@ -276,7 +276,7 @@ int itf14(struct zint_symbol *symbol, unsigned char source[])
 	source[h] = itoc(check_digit);
 	source[h + 1] = '\0';
 	error_number = interleaved_two_of_five(symbol, source);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -312,7 +312,7 @@ int dpleit(struct zint_symbol *symbol, unsigned char source[])
 	source[h] = itoc(check_digit);
 	source[h + 1] = '\0';
 	error_number = interleaved_two_of_five(symbol, source);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -347,6 +347,6 @@ int dpident(struct zint_symbol *symbol, unsigned char source[])
 	source[h] = itoc(check_digit);
 	source[h + 1] = '\0';
 	error_number = interleaved_two_of_five(symbol, source);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
diff --git a/backend/code.c b/backend/code.c
index ca8ce69f..1bcb91f8 100644
--- a/backend/code.c
+++ b/backend/code.c
@@ -146,7 +146,7 @@ int code_11(struct zint_symbol *symbol, unsigned char source[])
 	source[h + 1] = itoc(k_digit);
 	source[h + 2] = '\0';
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -233,10 +233,10 @@ int c39(struct zint_symbol *symbol, unsigned char source[])
 	
 	if(symbol->symbology == BARCODE_CODE39) {
 		strcpy(symbol->text, "*");
-		concat(symbol->text, source);
+		concat(symbol->text, (char*)source);
 		concat(symbol->text, "*");
 	} else {
-		strcpy(symbol->text, source);
+		strcpy(symbol->text, (char*)source);
 	}
 	return error_number;
 }
@@ -277,7 +277,7 @@ int pharmazentral(struct zint_symbol *symbol, unsigned char source[])
 	source[h + 1] = itoc(check_digit);
 	source[h + 2] = '\0';
 	error_number = c39(symbol, source);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -287,12 +287,12 @@ int pharmazentral(struct zint_symbol *symbol, unsigned char source[])
 int ec39(struct zint_symbol *symbol, unsigned char source[])
 { /* Extended Code 39 - ISO/IEC 16388:2007 Annex A */
 
-	char buffer[100];
+	unsigned char buffer[100];
 	unsigned int i;
-	strcpy(buffer, "");
 	int ascii_value;
 	int error_number;
-	
+
+	memset(buffer,0,100);
 	error_number = 0;
 
 	if(ustrlen(source) > 45) {
@@ -315,13 +315,13 @@ int ec39(struct zint_symbol *symbol, unsigned char source[])
 	/* Creates a buffer string and places control characters into it */
 	for(i = 0; i < ustrlen(source); i++) {
 		ascii_value = source[i];
-		concat(buffer, EC39Ctrl[ascii_value]);
+		concat((char*)buffer, EC39Ctrl[ascii_value]);
 	}
 
 	/* Then sends the buffer to the C39 function */
 	error_number = c39(symbol, buffer);
 	
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
 
@@ -434,6 +434,6 @@ int c93(struct zint_symbol *symbol, unsigned char source[])
 	source[h + 1] = set_copy[k];
 	source[h + 2] = '\0';
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return error_number;
 }
diff --git a/backend/code128.c b/backend/code128.c
index f247b55a..934a8953 100644
--- a/backend/code128.c
+++ b/backend/code128.c
@@ -566,7 +566,7 @@ int code_128(struct zint_symbol *symbol, unsigned char source[])
 	/* Stop character */
 	concat(dest, C128Table[106]);
 	expand(symbol, dest);
-	strcpy(symbol->text, source);
+	strcpy(symbol->text, (char*)source);
 	return errornum;
 }
 
@@ -904,9 +904,9 @@ int ean_14(struct zint_symbol *symbol, unsigned char source[])
 	/* EAN-14 - A version of EAN-128 */
 	int input_length, i, count, check_digit;
 	int error_number;
-	char ean128_equiv[20];
+	unsigned char ean128_equiv[20];
 	
-	strcpy(ean128_equiv, "");
+	memset(ean128_equiv, 0, 20);
 	input_length = ustrlen(source);
 	
 	if(input_length != 13) {
@@ -919,8 +919,8 @@ int ean_14(struct zint_symbol *symbol, unsigned char source[])
 		strcpy(symbol->errtxt, "error: invalid character in data");
 		return error_number;
 	}
-	concat(ean128_equiv, "[01]");
-	concat(ean128_equiv, source);
+	concat((char*)ean128_equiv, "[01]");
+	concat((char*)ean128_equiv, (char*)source);
 	
 	count = 0;
 	for (i = input_length - 1; i >= 0; i--)
diff --git a/backend/library.c b/backend/library.c
index e65058dc..6c3fb41f 100644
--- a/backend/library.c
+++ b/backend/library.c
@@ -110,7 +110,7 @@ extern int daft_code(struct zint_symbol *symbol, unsigned char source[]); /* DAF
 extern int ean_14(struct zint_symbol *symbol, unsigned char source[]); /* EAN-14 */
 
 #ifndef NO_PNG
-extern int png_plot(struct zint_symbol *symbol);
+int png_handle(struct zint_symbol *symbol, int rotate_angle);
 #endif
 
 extern int ps_plot(struct zint_symbol *symbol);
@@ -256,7 +256,7 @@ int ZBarcode_Print(struct zint_symbol *symbol)
 		output[1] = symbol->outfile[strlen(symbol->outfile) - 2];
 		output[2] = symbol->outfile[strlen(symbol->outfile) - 1];
 		output[3] = '\0';
-		to_upper(output);
+		to_upper((unsigned char*)output);
 #ifndef NO_PNG
 		if(!(strcmp(output, "PNG"))) {
 			error_number = png_handle(symbol, 0);
@@ -289,7 +289,7 @@ int ZBarcode_Print_Rotated(struct zint_symbol *symbol, int rotate_angle)
 		output[1] = symbol->outfile[strlen(symbol->outfile) - 2];
 		output[2] = symbol->outfile[strlen(symbol->outfile) - 1];
 		output[3] = '\0';
-		to_upper(output);
+		to_upper((unsigned char*)output);
 #ifndef NO_PNG
 		if(!(strcmp(output, "PNG"))) {
 			error_number = png_handle(symbol, rotate_angle);