1.0.0-rc2: Fixes in preview

preview/PreviewImage.cpp

@@ -33,6 +33,7 @@ constexpr const static rgb gray = {.r = 0xbe, .g = 0xbe, .b = 0xbe};
 
 PreviewImage::PreviewImage(const DiffractionExperiment &in_experiment) :
         experiment(in_experiment),
+        initialized(false),
         xpixel(experiment.GetXPixelsNum()),
         ypixel(experiment.GetYPixelsNum()),
         beam_x(experiment.GetBeamX_pxl()),
@@ -47,6 +48,7 @@ void PreviewImage::UpdateImage(const void *in_uncompressed_image,
                                const std::vector<SpotToSave> &in_spots) {
     if (counter.GeneratePreview()) {
         std::unique_lock<std::mutex> ul(m);
+        initialized = true;
         memcpy(uncompressed_image.data(), in_uncompressed_image, xpixel * ypixel * pixel_depth_bytes);
         spots = in_spots;
     }
@@ -109,6 +111,10 @@ std::string PreviewImage::GenerateJPEG(const PreviewJPEGSettings &settings) cons
     {
         // JPEG compression is outside the critical loop protected by m
         std::unique_lock<std::mutex> ul(m);
+
+        if (!initialized)
+            return {};
+
         if (!pixel_is_signed) {
             if (pixel_depth_bytes == 2)
                 v = GenerateRGB<uint16_t>((uint16_t *) uncompressed_image.data(), xpixel * ypixel,
@@ -141,6 +147,9 @@ std::string PreviewImage::GenerateJPEG(const PreviewJPEGSettings &settings) cons
 
 std::string PreviewImage::GenerateTIFF() const {
     std::unique_lock<std::mutex> ul(m);
+    if (!initialized)
+        return {};
+
     std::string s = WriteTIFFToString(const_cast<uint8_t *>(uncompressed_image.data()),
                                       xpixel, ypixel, pixel_depth_bytes, pixel_is_signed);
     return s;
@@ -167,6 +176,8 @@ std::vector<uint16_t> GenerateDioptasPreview(const void* input, size_t xpixel, s
 
 std::string PreviewImage::GenerateTIFFDioptas() const {
     std::unique_lock<std::mutex> ul(m);
+    if (!initialized)
+        return {};
 
     std::vector<uint16_t> vec;
     if (pixel_is_signed) {