Index: openacs-4/packages/captcha/captcha.info
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/captcha/captcha.info,v
diff -u -r1.1.2.3 -r1.1.2.4
--- openacs-4/packages/captcha/captcha.info	13 Jul 2023 13:12:31 -0000	1.1.2.3
+++ openacs-4/packages/captcha/captcha.info	13 Oct 2023 06:27:19 -0000	1.1.2.4
@@ -9,7 +9,7 @@
     <implements-subsite-p>f</implements-subsite-p>
     <inherit-templates-p>f</inherit-templates-p>
 
-    <version name="0.2" url="http://openacs.org/repository/download/apm/captcha-0.2.apm">
+    <version name="0.3.0" url="http://openacs.org/repository/download/apm/captcha-0.3.0apm">
         <owner url="mailto:antonio@elettrotecnica.it">Antonio Pisano</owner>
         <summary>A captcha implementation for the template system</summary>
         <release-date>2022-06-26</release-date>
@@ -22,13 +22,16 @@
         work on macOS</description>
         <maturity>0</maturity>
 
-        <provides url="captcha" version="0.2"/>
+        <provides url="captcha" version="0.3.0"/>
         <requires url="acs-templating" version="5.10.1b1"/>
-        
+
         <callbacks>
         </callbacks>
         <parameters>
-        <!-- No version parameters -->
+            <parameter scope="global" datatype="string"  min_n_values="1"  max_n_values="1"  name="backend"  default="convert" description="Decide the preferred implementation to use when generating the captcha. There are 2 options:
+
+ 1) &#34;tclgd&#34;: more performant, but needs to be installed on the machine
+ 2) &#34;convert&#34;: uses the widespread convert tool via exec"/>
         </parameters>
 
     </version>
Index: openacs-4/packages/captcha/tcl/captcha-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/captcha/tcl/captcha-procs.tcl,v
diff -u -r1.1.2.6 -r1.1.2.7
--- openacs-4/packages/captcha/tcl/captcha-procs.tcl	29 Aug 2023 14:10:37 -0000	1.1.2.6
+++ openacs-4/packages/captcha/tcl/captcha-procs.tcl	13 Oct 2023 06:27:19 -0000	1.1.2.7
@@ -143,6 +143,35 @@
     close $wfd
 }
 
+ad_proc -private captcha::backend {} {
+    @return the captcha backend used to generate the image
+} {
+    set backend [::parameter::get_global_value \
+                     -package_key captcha \
+                     -parameter backend \
+                     -default tclgd]
+    if {$backend eq "tclgd"} {
+        try {
+            package require tclgd
+        } on error {errmsg} {
+            ad_log warning \
+                "Cannot load tclgd library:" \
+                $errmsg \
+                "Falling back to convert implementation."
+            set backend "convert"
+        }
+    }
+
+    if {$backend eq "convert"} {
+        set convert [::util::which convert]
+        if {$convert eq ""} {
+            error {'tclgd' or 'convert' command not available.}
+        }
+    }
+
+    return $backend
+}
+
 ad_proc -private captcha::image::generate {
     {-size 150x50}
     -text
@@ -163,17 +192,7 @@
             text the image represents) and checksum (a checksum for
             the image to use for matching).
 } {
-    try {
-        package require tclgd
-    } on error {errmsg} {
-        set convert [::util::which convert]
-        if {$convert eq ""} {
-            error {'tclgd' or 'convert' command not available.}
-        }
-        set backend convert
-    } on ok {d} {
-        set backend tclgd
-    }
+    set backend [::captcha::backend]
 
     if {![regexp -nocase {^(\d+)x(\d+)$} $size m width height]} {
         error {Invalid size}