feat: return generation metadata with core results (#2206)

examples/common/media_metadata.cpp

@@ -0,0 +1,47 @@
+#include "media_metadata.h"
+
+std::string generation_xmp(const std::string& info) {
+    std::string escaped;
+    for (char c : info) {
+        switch (c) {
+            case '&':
+                escaped += "&";
+                break;
+            case '<':
+                escaped += "&lt;";
+                break;
+            case '>':
+                escaped += "&gt;";
+                break;
+            case '"':
+                escaped += "&quot;";
+                break;
+            case '\'':
+                escaped += "&apos;";
+                break;
+            default:
+                escaped += c;
+                break;
+        }
+    }
+    return "<x:xmpmeta xmlns:x=\"adobe:ns:meta/\"><rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\">"
+           "<rdf:Description rdf:about=\"\" xmlns:sdcpp=\"https://github.com/leejet/stable-diffusion.cpp/ns/1.0/\">"
+           "<sdcpp:parameters>" +
+           escaped + "</sdcpp:parameters></rdf:Description></rdf:RDF></x:xmpmeta>";
+}
+
+bool embed_jpeg_metadata(std::vector<uint8_t>& image, const std::string& parameters) {
+    if (parameters.empty())
+        return true;
+    const char label[]    = "parameters";
+    const size_t overhead = sizeof(label) + 1;
+    if (image.size() < 2 || parameters.size() > 65533 - overhead)
+        return false;
+    const size_t length          = overhead + parameters.size() + 2;
+    std::vector<uint8_t> segment = {0xff, 0xfe, static_cast<uint8_t>(length >> 8), static_cast<uint8_t>(length)};
+    segment.insert(segment.end(), label, label + sizeof(label));
+    segment.insert(segment.end(), parameters.begin(), parameters.end());
+    segment.push_back(0);
+    image.insert(image.begin() + 2, segment.begin(), segment.end());
+    return true;
+}