From f33522ac46a16963565076b996eca2ca6409843e Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Sat, 8 Feb 2025 11:45:13 -0500
Subject: [PATCH] Restore CompressConfig until qpdf 12

---
 include/qpdf/Pl_DCT.hh | 18 ++++++++++++++++--
 libqpdf/Pl_DCT.cc      | 17 +++++++++++++----
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/include/qpdf/Pl_DCT.hh b/include/qpdf/Pl_DCT.hh
index 1f63f93..1af9d36 100644
--- a/include/qpdf/Pl_DCT.hh
+++ b/include/qpdf/Pl_DCT.hh
@@ -52,6 +52,16 @@ class QPDF_DLL_CLASS Pl_DCT: public Pipeline
     QPDF_DLL
     static void setThrowOnCorruptData(bool treat_as_error);
 
+    class QPDF_DLL_CLASS CompressConfig
+    {
+      public:
+        QPDF_DLL
+        CompressConfig() = default;
+        QPDF_DLL
+        virtual ~CompressConfig() = default;
+        virtual void apply(jpeg_compress_struct*) = 0;
+    };
+
     // Constructor for compressing image data
     QPDF_DLL
     Pl_DCT(
@@ -60,7 +70,8 @@ class QPDF_DLL_CLASS Pl_DCT: public Pipeline
         JDIMENSION image_width,
         JDIMENSION image_height,
         int components,
-        J_COLOR_SPACE color_space);
+        J_COLOR_SPACE color_space,
+        CompressConfig* config_callback = nullptr);
 
     QPDF_DLL
     ~Pl_DCT() override;
@@ -93,7 +104,8 @@ class QPDF_DLL_CLASS Pl_DCT: public Pipeline
             JDIMENSION image_width,
             JDIMENSION image_height,
             int components,
-            J_COLOR_SPACE color_space);
+            J_COLOR_SPACE color_space,
+            CompressConfig* config_callback);
         // For decompression
         Members();
 
@@ -105,6 +117,8 @@ class QPDF_DLL_CLASS Pl_DCT: public Pipeline
         JDIMENSION image_height{0};
         int components{1};
         J_COLOR_SPACE color_space{JCS_GRAYSCALE};
+
+        CompressConfig* config_callback{nullptr};
     };
 
     std::shared_ptr<Members> m;
diff --git a/libqpdf/Pl_DCT.cc b/libqpdf/Pl_DCT.cc
index f7b37a2..047cacb 100644
--- a/libqpdf/Pl_DCT.cc
+++ b/libqpdf/Pl_DCT.cc
@@ -64,13 +64,18 @@ Pl_DCT::Members::Members() :
 }
 
 Pl_DCT::Members::Members(
-    JDIMENSION image_width, JDIMENSION image_height, int components, J_COLOR_SPACE color_space) :
+    JDIMENSION image_width,
+    JDIMENSION image_height,
+    int components,
+    J_COLOR_SPACE color_space,
+    CompressConfig* config_callback) :
     action(a_compress),
     buf("DCT uncompressed image"),
     image_width(image_width),
     image_height(image_height),
     components(components),
-    color_space(color_space)
+    color_space(color_space),
+    config_callback(config_callback)
 {
 }
 
@@ -107,9 +112,10 @@ Pl_DCT::Pl_DCT(
     JDIMENSION image_width,
     JDIMENSION image_height,
     int components,
-    J_COLOR_SPACE color_space) :
+    J_COLOR_SPACE color_space,
+    CompressConfig* compress_callback) :
     Pipeline(identifier, next),
-    m(new Members(image_width, image_height, components, color_space))
+    m(new Members(image_width, image_height, components, color_space, compress_callback))
 {
 }
 
@@ -310,6 +316,9 @@ Pl_DCT::compress(void* cinfo_p, Buffer* b)
     cinfo->input_components = m->components;
     cinfo->in_color_space = m->color_space;
     jpeg_set_defaults(cinfo);
+    if (m->config_callback) {
+        m->config_callback->apply(cinfo);
+    }
 
     jpeg_start_compress(cinfo, TRUE);
 
--
libgit2 0.21.4