feat: implement cpp functions to get and set exif data

2 files changed, 86 insertions, 0 deletions

diff --git a/lib/exif_wrapper.cpp b/lib/exif_wrapper.cpp
new file mode 100644
index 0000000..e6b60b1
--- /dev/null
+++ b/lib/exif_wrapper.cpp
@@ -0,0 +1,82 @@
+#include <cstdio>
+#include <exiv2/exiv2.hpp>
+#include <cassert>
+#include <exiv2/image.hpp>
+#include <memory>
+#include <string>
+
+#include <unistd.h>
+
+const char* ORIENTATION_KEY = "Exif.Image.Orientation";
+
+
+extern "C" unsigned int getExifOrientation(uint8_t* imgBytes, unsigned int size) {
+    try {
+        Exiv2::XmpParser::initialize();
+        ::atexit(Exiv2::XmpParser::terminate);
+        Exiv2::enableBMFF();
+
+        Exiv2::Image::AutoPtr image = Exiv2::ImageFactory::open(imgBytes, size);
+        assert(image.get() != 0);
+        image->readMetadata();
+
+        Exiv2::ExifData &exifData = image->exifData();
+        if (exifData.empty()) {
+            return 9;
+        }
+
+        return (unsigned int) exifData[ORIENTATION_KEY].toLong();
+    }
+    //catch (std::exception& e) {
+    //catch (Exiv2::AnyError& e) {
+    catch (Exiv2::Error& e) {
+        std::cout << "Caught Exiv2 exception '" << e.what() << "'\n";
+        return 9;
+    }
+}
+
+extern "C" void setExifOrientation(uint8_t* imgBytes, unsigned int size, unsigned int orientation) {
+        int chk = 0;
+        for (int i = 0; i < size; i++) {
+            chk = (chk + (int)imgBytes[i] * 13) % 100000;
+        }
+        printf("start chk:%d\n",chk);
+    try {
+        // Hack to work around Exiv2 seeming to refuse to write back to blob, but will write
+        // back to a file. Create temp file -> operate on it -> copy back to blob, unlink file.
+        char tmpFileName[] = "/tmp/image-temp.XXXXXX";
+        int fd = mkstemp(tmpFileName);
+        assert(fd != -1);
+        write(fd, imgBytes, size);
+        close(fd);
+
+        // Exiv init
+        Exiv2::XmpParser::initialize();
+        ::atexit(Exiv2::XmpParser::terminate);
+        Exiv2::enableBMFF();
+
+
+        // using blob works, except that exiv2 won't write back to the blob :(
+        //  std::unique_ptr<Exiv2::Image> image = Exiv2::ImageFactory::open(imgBytes, size);
+        // So instead we load from the temp file
+        std::unique_ptr<Exiv2::Image> image = Exiv2::ImageFactory::open(tmpFileName);
+        assert(image.get() != 0);
+        image->readMetadata();
+        Exiv2::ExifData &exifData = image->exifData();
+
+        exifData[ORIENTATION_KEY] = orientation;
+
+        // Save exif to image object & save image back to file
+        image->setExifData(exifData);
+        image->writeMetadata();
+
+        // reopen temp file, copy result back into byte array
+        FILE* fileptr = fopen(tmpFileName, "rb");
+        fread(imgBytes, size, 1, fileptr);
+        fclose(fileptr);
+        unlink(tmpFileName);
+    }
+    catch (Exiv2::Error& e) {
+        std::cout << "Caught Exiv2 exception '" << e.what() << "'\n";
+    }
+}
diff --git a/lib/exif_wrapper.h b/lib/exif_wrapper.h
new file mode 100644
index 0000000..ec51406
--- /dev/null
+++ b/lib/exif_wrapper.h
@@ -0,0 +1,4 @@
+#include <stdint.h>
+
+unsigned int getExifOrientation(uint8_t* imgBytes, unsigned int size);
+void setExifOrientation(uint8_t* imgBytes, unsigned int size, unsigned int orientation);