.ssp digests: report missing or unreadable image

image digest: record missing or unreadable image, do not abort

safeComputeHashAndSize() open image with guard, so a document
naming an image absent from media/image/ throws
ErrnoException out of the abstraction stage.

as with _image_dimensions() (which warns and continues where issue
with image) warn to stdout and record the fact in the abstraction:

  .image: ffa.png missing:true

the abstraction would now state that the object embeds an image it
could not read, rather than the .ssp resemble one produced from a
complete pod. The sha256 summary line marks the same case
MISSING OR UNREADABLE.

(assisted by Claude-Code)

5 files changed, 45 insertions, 14 deletions

diff --git a/org/ocda_functions.org b/org/ocda_functions.org
index 37a4f6f..4745bc5 100644
--- a/org/ocda_functions.org
+++ b/org/ocda_functions.org
@@ -3431,13 +3431,23 @@ SHA_256_Hashes_ obj_digest(M)(
 ) {
   ST_file_name_hash_size_ safeComputeHashAndSize(N,P)(N filename, P file_path) @trusted {
     auto file_with_path = file_path ~ filename;
-    auto file_read = File(file_with_path, "r");
-    ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
-    ulong fileSize = file_read.size;
     ST_file_name_hash_size_ _file_info;
-    _file_info.fileHash_sha256 = file_sha256;
-    _file_info.fileSize = fileSize;
     _file_info.fileName = filename;
+    /+ ↓ a referenced image that is absent or unreadable is recorded as
+       such rather than aborting the abstraction (compare the WARNING
+       issued by _image_dimensions for the same situation)
+    +/
+    try {
+      auto file_read = File(file_with_path, "r");
+      ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
+      ulong fileSize = file_read.size;
+      _file_info.fileHash_sha256 = file_sha256;
+      _file_info.fileSize = fileSize;
+    } catch (Exception ex) {
+      _file_info.fileMissing = true;
+      writeln("WARNING, image not found or unreadable: ", filename,
+        "\n  ", file_with_path);
+    }
     return _file_info;
   }
   obj.metainfo.sha256.text = obj.text.sha256Of;
@@ -3464,7 +3474,9 @@ SHA_256_Hashes_ obj_digest(M)(
     char[] image_summary;
     if (obj.metainfo.sha256.images.length > 0) {
       foreach (i; obj.metainfo.sha256.images) {
-        image_summary ~= "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
+        image_summary ~= (i.fileMissing)
+        ? "\n     - " ~ "MISSING OR UNREADABLE" ~ " - " ~ i.fileName
+        : "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
       }
     }
     obj.metainfo.sha256.summary ~=
diff --git a/org/ocda_obj_setter.org b/org/ocda_obj_setter.org
index f419954..8e7a67c 100644
--- a/org/ocda_obj_setter.org
+++ b/org/ocda_obj_setter.org
@@ -53,6 +53,7 @@ struct ST_file_name_hash_size_ {
   string    fileName;
   ubyte[32] fileHash_sha256;
   ulong     fileSize;
+  bool      fileMissing        = false; // file not found or unreadable, fileHash_sha256 & fileSize unset
 }
 struct SHA_256_Hashes_ {
   char[]                 summary;
diff --git a/org/out_src_abstraction_ocda_ssp.org b/org/out_src_abstraction_ocda_ssp.org
index 2d8b128..d2bb8a4 100644
--- a/org/out_src_abstraction_ocda_ssp.org
+++ b/org/out_src_abstraction_ocda_ssp.org
@@ -275,7 +275,10 @@ template spineAbstractionTxt() {
         +/
         if (obj.metainfo.sha256.images.length > 0) {
           foreach (i; obj.metainfo.sha256.images) {
-            output ~= ".image: "  ~ i.fileName
+            output ~= (i.fileMissing)
+            ? ".image: "          ~ i.fileName
+              ~ " missing:true"
+            : ".image: "          ~ i.fileName
               ~ " sha256:"        ~ i.fileHash_sha256.toHexString.to!string
               ~ " bytes:"         ~ i.fileSize.to!string;
           }
diff --git a/src/sisudoc/ocda/abstraction/ssp.d b/src/sisudoc/ocda/abstraction/ssp.d
index 95f7fda..ea76d71 100644
--- a/src/sisudoc/ocda/abstraction/ssp.d
+++ b/src/sisudoc/ocda/abstraction/ssp.d
@@ -293,7 +293,10 @@ template spineAbstractionTxt() {
         +/
         if (obj.metainfo.sha256.images.length > 0) {
           foreach (i; obj.metainfo.sha256.images) {
-            output ~= ".image: "  ~ i.fileName
+            output ~= (i.fileMissing)
+            ? ".image: "          ~ i.fileName
+              ~ " missing:true"
+            : ".image: "          ~ i.fileName
               ~ " sha256:"        ~ i.fileHash_sha256.toHexString.to!string
               ~ " bytes:"         ~ i.fileSize.to!string;
           }
diff --git a/src/sisudoc/ocda/meta/metadoc_from_src_functions.d b/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
index 791c002..6e4aec3 100644
--- a/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
+++ b/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
@@ -3191,13 +3191,23 @@ template docAbstractionFunctions() {
   ) {
     ST_file_name_hash_size_ safeComputeHashAndSize(N,P)(N filename, P file_path) @trusted {
       auto file_with_path = file_path ~ filename;
-      auto file_read = File(file_with_path, "r");
-      ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
-      ulong fileSize = file_read.size;
       ST_file_name_hash_size_ _file_info;
-      _file_info.fileHash_sha256 = file_sha256;
-      _file_info.fileSize = fileSize;
       _file_info.fileName = filename;
+      /+ ↓ a referenced image that is absent or unreadable is recorded as
+         such rather than aborting the abstraction (compare the WARNING
+         issued by _image_dimensions for the same situation)
+      +/
+      try {
+        auto file_read = File(file_with_path, "r");
+        ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
+        ulong fileSize = file_read.size;
+        _file_info.fileHash_sha256 = file_sha256;
+        _file_info.fileSize = fileSize;
+      } catch (Exception ex) {
+        _file_info.fileMissing = true;
+        writeln("WARNING, image not found or unreadable: ", filename,
+          "\n  ", file_with_path);
+      }
       return _file_info;
     }
     obj.metainfo.sha256.text = obj.text.sha256Of;
@@ -3224,7 +3234,9 @@ template docAbstractionFunctions() {
       char[] image_summary;
       if (obj.metainfo.sha256.images.length > 0) {
         foreach (i; obj.metainfo.sha256.images) {
-          image_summary ~= "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
+          image_summary ~= (i.fileMissing)
+          ? "\n     - " ~ "MISSING OR UNREADABLE" ~ " - " ~ i.fileName
+          : "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
         }
       }
       obj.metainfo.sha256.summary ~=