/*
* This function displays a 4-bit bitmap described by the
* BitmapData structure.
* It has one restriction.
* 1. The bitmap must be an even number of pixels wide.
*
* left, top is the location of the upper left dot
* of the bitmap on the display.
*/
void imageRender(const BitmapData * imagePtr, int left, int top)
{
/*
* x
and y will track the location we are
* drawing within the bitmap.
*/
unsigned int x,y;
/*
* index tracks our location within the array of bytes
* that represent the image.
*/
long index;
/*
* The value of pixel is the color of the dot
*/
unsigned char pixel;
/*
* Make sure that the bitmap does not go outside of the display.
*/
assert(top +
imagePtr->height
<
= DISPLAY_FULL_HEIGHT);
assert(left + imagePtr->width
<
= DISPLAY_FULL_WIDTH);
index = 0;
for (y = 0; y
<
imagePtr->height; y++)
{
/*
* x will step forward 2 at a time, since each
* byte contains 2 pixels
*/
for (x = 0; x
<
imagePtr->width; x += 2)
{
/*
* First extract the color of the next pixel
* from the high order nibble
*/
pixel =
imagePtr->raw[index] >> 4;
/*
* Now place a dot, with the color pixel in
* the next location on the display
*/
drawDot(x + left, y + top, pixel);
/*
* Next extract the color from the second pixel
* from the low order nibble
*/
pixel = imagePtr->raw[index] & (0x0F);
drawDot(x+1 + left, y + top, pixel);
/*
index increases once for every two dots drawn,
since we have two dots-per-pixel.
*/
index++;
}
}
}
