A good start

includes/kernel/util.c

@@ -0,0 +1,42 @@
+/**
+arm-016-util.c
+*/
+#include "util.h"
+
+void setColor(volatile unsigned char* fb, colour_t pixel, long x, long y, long pitch)
+{
+	int pixel_offset = ( x * ( SCREEN_DEPTH >> 3 ) ) + ( y * pitch );
+
+    int r = (int)( pixel.r * 0xFF ) & 0xFF;
+    int g = (int)( pixel.g * 0xFF ) & 0xFF;
+    int b = (int)( pixel.b * 0xFF ) & 0xFF;
+    int a = (int)( pixel.a * 0xFF ) & 0xFF;
+
+    if( SCREEN_DEPTH == 32 )
+    {
+        /* Four bytes to write */
+        fb[ pixel_offset++ ] = r;
+        fb[ pixel_offset++ ] = g;
+        fb[ pixel_offset++ ] = b;
+        fb[ pixel_offset++ ] = a;
+    }
+    else if( SCREEN_DEPTH == 24 )
+    {
+        /* Three bytes to write */
+        fb[ pixel_offset++ ] = r;
+        fb[ pixel_offset++ ] = g;
+        fb[ pixel_offset++ ] = b;
+    }
+    else if( SCREEN_DEPTH == 16 )
+    {
+        /* Two bytes to write */
+        /* Bit pack RGB565 into the 16-bit pixel offset */
+        *(unsigned short*)&fb[pixel_offset] = ( (r >> 3) << 11 ) | ( ( g >> 2 ) << 5 ) | ( b >> 3 );
+    }
+    else
+    {
+        /* Palette mode. TODO: Work out a colour scheme for
+           packing rgb into an 8-bit palette! */
+    }
+}
+

includes/kernel/util.h

@@ -0,0 +1,33 @@
+/**
+arm-016-util.h
+*/
+
+
+#ifndef arm_016_util
+#define arm_016_util
+
+#define SCREEN_WIDTH    1920
+#define SCREEN_HEIGHT   1080
+#define SCREEN_DEPTH    24      /* 16 or 32-bit */
+
+#define COLOUR_DELTA    0.05    /* Float from 0 to 1 incremented by this amount */
+
+typedef struct {
+    float r;
+    float g;
+    float b;
+    float a;
+    } colour_t;
+
+
+#define dickbuttHeight   352
+#define dickbuttWidth    624
+#define dickbuttBytes    658945
+
+extern const int dickbutt[dickbuttBytes];
+
+
+extern void setColor(volatile unsigned char* fb, colour_t pixel, long x, long y, long pitch);
+
+
+#endif