diff --git a/png2uri b/png2uri
index e74c5e5..8feba9d 100755
--- a/png2uri
+++ b/png2uri
@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# png2uri version 1.0.2, July 4, 2012.
+# png2uri version 1.0.3, July 5, 2012.
 #
 # NO COPYRIGHT RIGHTS ARE CLAIMED TO THIS SOFTWARE.
 #
@@ -23,8 +23,8 @@
 # png2uri is a command-line application that creates an HTML "img" tag on
 # standard output containing a data URI in accordance with RFC-2397, from
 # a PNG file or from a PNG datastream received from standard input.
-# Other formats besides the default, PNG, are supported, via the "-f or
-# --format option or, if that option was not supplied, by inspection of the
+# Other formats besides the default, PNG, are supported, via the "-f" or
+# "--format" option or, if that option was not supplied, by inspection of the
 # filename extension.
 #
 # Usage: png2uri [-f type|--format type] [-u|--uri_only] [file]
@@ -44,86 +44,100 @@
 # to encode in base64 according to RFC-3548, and a working "sed".
 #
 # If you prefer a web-based converter or a java application, this isn't
-# it. Use your search engine and look for "png data uri" to find one.
+# it. Use your search engine and look for "data uri" to find one.
 #
 
-uri_only="false"
-format="unknown"
+PNG2URI_URI="true"
+PNG2URI_FMT="unknown"
 
 while true
 do
-case x$1 in
-  x-f|x--format)
-      shift
-      case x$1 in
-         xpng|xPNG)
-           format=image/png
-         ;;
-         xjpeg|xJPEG|xjpg|xJPG)
-           format=image/jpeg
-         ;;
-         xbmp|xBMP)
-           format=image/bmp
-         ;;
-         xgif|xGIF)
-           format=image/gif
-         ;;
-         *)
-           format=$1
-         ;;
-      esac
+case X$1 in
+  X-f|X--format)
+    shift
+
+    case X$1 in
+      Xpng|XPNG)
+        PNG2URI_FMT=image/png
+        ;;
+
+      Xjpeg|XJPEG|Xjpg|XJPG)
+        PNG2URI_FMT=image/jpeg
+        ;;
+
+      Xbmp|XBMP)
+        PNG2URI_FMT=image/bmp
+        ;;
+
+      Xgif|XGIF)
+        PNG2URI_FMT=image/gif
+        ;;
+
+      *)
+        PNG2URI_FMT=$1
+        ;;
+    esac
+    shift
+    ;;
+
+  X-u|X--ur*)
+      PNG2URI_URI="false"
       shift
       ;;
-  x-u|x--ur*)
-      uri_only="true"
-      shift
-      ;;
-  x)
+
+  X)
       # Convert standard input.
-      case $format in
-        unknown)
-           format=image/png
-           ;;
+      case X$PNG2URI_FMT in
+        Xunknown)
+          PNG2URI_FMT=image/png
+          ;;
       esac
-      case $uri_only in
-         true)
-            echo "data:$format;base64,"
-            uuencode -m ==== | grep -v ====
-            ;;
-         false)
-            echo "<img alt=\"PNG\" title=\"PNG\" src=\"data:$format;base64,"
-            uuencode -m ==== | grep -v ====
-            echo "\">"
-            ;;
+
+      case X$PNG2URI_URI in
+        Xfalse)
+          echo "data:$PNG2URI_FMT;base64,"
+          uuencode -m ==== | grep -v ====
+          ;;
+
+        *)
+          echo "<img alt=\"PNG\" title=\"PNG\" src=\"data:$PNG2URI_FMT;base64,"
+          uuencode -m ==== | grep -v ====
+          echo "\">"
+          ;;
       esac
       exit
       ;;
+
   *)
       # Convert the named file.
-      case $format in
-        unknown)
-           format=image/png
-           extension=`echo $1 | sed "s/.*\.//"`
-           case x$extension in
-              xjpeg|xJPEG|xjpg|xJPG)
-                format=image/jpeg
-              ;;
-              xbmp|xBMP)
-                format=image/bmp
-              ;;
-              xgif|xGIF)
-                format=image/gif
-              ;;
+      case X$PNG2URI_FMT in
+        Xunknown)
+          PNG2URI_FMT=image/png
+          extension=`echo $1 | sed "s/.*\.//"`
+
+          case X$extension in
+              Xjpeg|XJPEG|Xjpg|XJPG)
+                PNG2URI_FMT=image/jpeg
+                ;;
+
+              Xbmp|XBMP)
+                PNG2URI_FMT=image/bmp
+                ;;
+
+              Xgif|XGIF)
+                PNG2URI_FMT=image/gif
+                ;;
             esac
-         ;;
+          ;;
       esac
-      case $uri_only in
-         true)
-            echo "data:$format;base64,"
+
+      case X$PNG2URI_URI in
+        Xfalse)
+            echo "data:$PNG2URI_FMT;base64,"
             uuencode -m $1 ==== | grep -v ====
             ;;
-         false)
-            echo "<img alt=\"$1\" title=\"$1\" src=\"data:$format;base64,"
+        *)
+            echo "<img alt=\"$1\" title=\"$1\" src=\"data:$PNG2URI_FMT;base64,"
             uuencode -m $1 ==== | grep -v ====
             echo "\">"
             ;;
diff --git a/png2uri-README.txt b/png2uri-README.txt
index f9f4f7d..19e4823 100644
--- a/png2uri-README.txt
+++ b/png2uri-README.txt
@@ -21,8 +21,8 @@
 
  png2uri is a command-line application that creates an HTML "img" tag on
  standard output containing a data URI, from a PNG file or from standard
- input. Other formats besides the default, PNG, are supported, via the "-f
- or --format option or, if that option was not supplied, by inspection of
+ input. Other formats besides the default, PNG, are supported, via the "-f"
+ or "--format" option or, if that option was not supplied, by inspection of
  the filename extension.
 
  Usage: png2uri [-f format|--format format] [-u|--uri_only] [file]
@@ -93,6 +93,12 @@
 
       Implemented "-f TYPE" and "--format TYPE" option.
 
+   Version 1.0.3, July 5, 2012:
+
+      Changed environment variable "format" to PNG2URI_FMT reduce possibility`
+      of name conflict, and changed "uri_only" to PNG2URI_URI.  Fixed some
+      indentation.
+
  TO DO
 
  1. Test on various platforms. The following have been tried