change pixel data to be unsigned

OLEDDisplay.cpp

@@ -347,11 +347,11 @@ void OLEDDisplay::drawProgressBar(uint16_t x, uint16_t y, uint16_t width, uint16
   fillCircle(xRadius + maxProgressWidth, yRadius, innerRadius);
 }
 
-void OLEDDisplay::drawFastImage(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const char *image) {
+void OLEDDisplay::drawFastImage(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const unsigned char *image) {
   drawInternal(xMove, yMove, width, height, image, 0, 0);
 }
 
-void OLEDDisplay::drawXbm(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const char *xbm) {
+void OLEDDisplay::drawXbm(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const unsigned char *xbm) {
   int16_t widthInXbm = (width + 7) / 8;
   uint8_t data;
 

OLEDDisplay.h

@@ -155,10 +155,10 @@ class OLEDDisplay : public Print {
     void drawProgressBar(uint16_t x, uint16_t y, uint16_t width, uint16_t height, uint8_t progress);
 
     // Draw a bitmap in the internal image format
-    void drawFastImage(int16_t x, int16_t y, int16_t width, int16_t height, const char *image);
+    void drawFastImage(int16_t x, int16_t y, int16_t width, int16_t height, const unsigned char *image);
 
     // Draw a XBM
-    void drawXbm(int16_t x, int16_t y, int16_t width, int16_t height, const char *xbm);
+    void drawXbm(int16_t x, int16_t y, int16_t width, int16_t height, const unsigned char *xbm);
 
     /* Text functions */