diff --git a/common/event_monitor.h b/common/event_monitor.h
index 9900bb5..1211aa9 100644
--- a/common/event_monitor.h
+++ b/common/event_monitor.h
@@ -25,10 +25,7 @@ enum scanner_event
     SCANNER_EVENT_COLLECTOR_WORKING = 100,		// on_event(, nullptr, 0), the first message after start success
 
     // normal image, double feeding image, jammed image, stapled imge, size-check error image ...
-    SCANNER_EVENT_COLLECTOR_IMG_BEGIN,			// on_event(, LPPACKIMAGE/*data_size can be ZERO*/, (bool)local_display/*show mesaage to local-liquid-crystal screen*/), start a new image data transferring
-    SCANNER_EVENT_COLLECOTR_GET_BUF,            // on_event(, LPREQBUF, len)
-    SCANNER_EVENT_COLLECTOR_IMG_DATA,			// on_event(, (uint8_t*)data, bytes of data), image data transfer
-    SCANNER_EVENT_COLLECTOR_IMG_END,			// on_event(, LPPACKIMAGE, sizeof(PACKIMAGE)), an image data has been transmitted
+    SCANNER_EVENT_COLLECTOR_IMG_DATA,			// on_event(, (LPIMGD)data, bytes of data), image data transfer, buffer can be re-used when return
 
     SCANNER_EVENT_COLLECTOR_PAPER_ON,			// on_event(, (bool*)paper_on, (bool)local_display)
     SCANNER_EVENT_COLLECTOR_COVER_OPENNED,		// on_event(, (bool*)openned, (bool)local_display)
@@ -48,11 +45,13 @@ enum scanner_event
     SCANNER_EVENT_RESOURCE_HIGH_CPU,
 };
 
-typedef struct _req_buf
+typedef struct _img_data
 {
-    size_t  len;
-    uint8_t* buf;
-}REQBUF, *LPREQBUF;
+    uint32_t    new_img : 1;                    // 0 - partial data; 1 - new image data
+    uint32_t    img_over : 1;                   // 0 - has data yet; 1 - END for the image
+    uint32_t    reserve : 30;
+    uint8_t*    buf;
+}IMGD, *LPIMGD;
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 // object event_handler