Got it almost working...

src/P700Printer.cpp

@@ -123,21 +123,23 @@ bool P700Printer::detachUsbDevice() {
 }
 
 bool P700Printer::printBitmap(const graphics::Bitmap<graphics::ALPHA8>& bitmap) {
-    auto bm = graphics::Bitmap<graphics::ALPHA8>(512, 128);
-    {
-        auto img = graphics::Label();
-        bm.setPixels(std::vector<uint8_t>(img.getRaw(), img.getRaw() + 512 * 128));
+#ifdef DRYRUN
+    SPDLOG_DEBUG("DRYRUN enabled");
+    for (unsigned int lineNo = 0; lineNo < bitmap.getHeight(); lineNo++) {
+        auto line     = bitmap.getLine(lineNo);
+        auto monoLine = graphics::Monochrome(*line);
+        monoLine.visualize();
     }
+#endif
 
     send(commands["rasterstart"]);
-
     std::vector<uint8_t> rastercmd(4);
     rastercmd[0] = 0x47;
     rastercmd[1] = 0x00;  // size +1
     rastercmd[2] = 0x00;
     rastercmd[3] = 0x00;  // size -1
-    for (unsigned int i = 0; i < bm.getWidth(); i++) {
-        auto bmcol = bm.getCol(i);
+    for (unsigned int i = 0; i < bitmap.getWidth(); i++) {
+        auto bmcol = bitmap.getCol(i);
         if (!bmcol) {
             spdlog::error("Out of bounds bitmap access");
             break;
@@ -152,6 +154,7 @@ bool P700Printer::printBitmap(const graphics::Bitmap<graphics::ALPHA8>& bitmap)
         buf[1] = col.size() + 1;
         buf[3] = col.size() - 1;
         if (!send(buf)) {
+            spdlog::error("Error sending buffer to printer");
             break;
         };
     }
@@ -203,11 +206,11 @@ bool P700Printer::send(std::vector<uint8_t>& data) {
     }
 #else
     tx = data.size();
-    SPDLOG_DEBUG("USB raw data(len {}): {}", data.size(), spdlog::to_hex(data));
+    spdlog::info("USB raw data(len {}): {}", data.size(), spdlog::to_hex(data));
 #endif
 
     if (tx != static_cast<int>(data.size())) {
-        spdlog::error("Could not transfer all data via USB bulk transfer. Only send {} of {} bytes",
+        spdlog::error("Could not transfer all data via USB bulk transfer. Only sent {} of {} bytes",
                       tx, data.size());
         return false;
     }