line art (#5052)

## Summary
- introduce a shared line art conversion interface and proprietary
ImageMagick-backed implementation
- have the compress controller optionally autowire the enterprise
service before running per-image line art processing
- remove ImageMagick command details from core by delegating conversions
through the proprietary service

## Testing
- not run (not requested)


------
[Codex
Task](https://chatgpt.com/codex/tasks/task_b_6928aecceaf083289a9269b1ca99307e)

---------

Co-authored-by: James Brunton <jbrunton96@gmail.com>

app/common/src/main/java/stirling/software/SPDF/config/EndpointConfiguration.java

@@ -491,6 +491,9 @@ public class EndpointConfiguration {
         addEndpointToGroup("Ghostscript", "repair");
         addEndpointToGroup("Ghostscript", "compress-pdf");
 
+        /* ImageMagick */
+        addEndpointToGroup("ImageMagick", "compress-pdf");
+
         /* tesseract */
         addEndpointToGroup("tesseract", "ocr-pdf");
 
@@ -574,6 +577,7 @@ public class EndpointConfiguration {
                 || "Javascript".equals(group)
                 || "Weasyprint".equals(group)
                 || "Pdftohtml".equals(group)
+                || "ImageMagick".equals(group)
                 || "rar".equals(group);
     }
 

app/common/src/main/java/stirling/software/common/model/ApplicationProperties.java

@@ -653,6 +653,7 @@ public class ApplicationProperties {
             private int weasyPrintSessionLimit;
             private int installAppSessionLimit;
             private int calibreSessionLimit;
+            private int imageMagickSessionLimit;
             private int qpdfSessionLimit;
             private int tesseractSessionLimit;
             private int ghostscriptSessionLimit;
@@ -690,6 +691,10 @@ public class ApplicationProperties {
                 return calibreSessionLimit > 0 ? calibreSessionLimit : 1;
             }
 
+            public int getImageMagickSessionLimit() {
+                return imageMagickSessionLimit > 0 ? imageMagickSessionLimit : 4;
+            }
+
             public int getGhostscriptSessionLimit() {
                 return ghostscriptSessionLimit > 0 ? ghostscriptSessionLimit : 8;
             }
@@ -719,6 +724,8 @@ public class ApplicationProperties {
             @JsonProperty("calibretimeoutMinutes")
             private long calibreTimeoutMinutes;
 
+            private long imageMagickTimeoutMinutes;
+
             private long tesseractTimeoutMinutes;
             private long qpdfTimeoutMinutes;
             private long ghostscriptTimeoutMinutes;
@@ -756,6 +763,10 @@ public class ApplicationProperties {
                 return calibreTimeoutMinutes > 0 ? calibreTimeoutMinutes : 30;
             }
 
+            public long getImageMagickTimeoutMinutes() {
+                return imageMagickTimeoutMinutes > 0 ? imageMagickTimeoutMinutes : 30;
+            }
+
             public long getGhostscriptTimeoutMinutes() {
                 return ghostscriptTimeoutMinutes > 0 ? ghostscriptTimeoutMinutes : 30;
             }

app/common/src/main/java/stirling/software/common/service/LineArtConversionService.java

@@ -0,0 +1,12 @@
+package stirling.software.common.service;
+
+import java.io.IOException;
+
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
+
+public interface LineArtConversionService {
+    PDImageXObject convertImageToLineArt(
+            PDDocument doc, PDImageXObject originalImage, double threshold, int edgeLevel)
+            throws IOException;
+}

app/common/src/main/java/stirling/software/common/util/ProcessExecutor.java

@@ -86,6 +86,11 @@ public class ProcessExecutor {
                                                 .getProcessExecutor()
                                                 .getSessionLimit()
                                                 .getCalibreSessionLimit();
+                                case IMAGEMAGICK ->
+                                        applicationProperties
+                                                .getProcessExecutor()
+                                                .getSessionLimit()
+                                                .getImageMagickSessionLimit();
                                 case GHOSTSCRIPT ->
                                         applicationProperties
                                                 .getProcessExecutor()
@@ -141,6 +146,11 @@ public class ProcessExecutor {
                                                 .getProcessExecutor()
                                                 .getTimeoutMinutes()
                                                 .getCalibreTimeoutMinutes();
+                                case IMAGEMAGICK ->
+                                        applicationProperties
+                                                .getProcessExecutor()
+                                                .getTimeoutMinutes()
+                                                .getImageMagickTimeoutMinutes();
                                 case GHOSTSCRIPT ->
                                         applicationProperties
                                                 .getProcessExecutor()
@@ -301,6 +311,7 @@ public class ProcessExecutor {
         WEASYPRINT,
         INSTALL_APP,
         CALIBRE,
+        IMAGEMAGICK,
         TESSERACT,
         QPDF,
         GHOSTSCRIPT,