offscr4bpp.c

STM32+Grlib

//*****************************************************************************
//
// offscr4bpp.c - 4 BPP off-screen display buffer driver.
//
// Copyright (c) 2008-2010 Texas Instruments Incorporated.  All rights reserved.
// Software License Agreement
// 
// Texas Instruments (TI) is supplying this software for use solely and
// exclusively on TI's microcontroller products. The software is owned by
// TI and/or its suppliers, and is protected under applicable copyright
// laws. You may not combine this software with "viral" open-source
// software in order to form a larger program.
// 
// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
// DAMAGES, FOR ANY REASON WHATSOEVER.
// 
// This is part of revision 5821 of the Stellaris Graphics Library.
//
//*****************************************************************************

#include "driverlib/debug.h"
#include "grlib/grlib.h"

//*****************************************************************************
//
//! \addtogroup primitives_api
//! @{
//
//*****************************************************************************

//*****************************************************************************
//
//! Translates a 24-bit RGB color to a display driver-specific color.
//!
//! \param pvDisplayData is a pointer to the driver-specific data for this
//! display driver.
//! \param ulValue is the 24-bit RGB color.  The least-significant byte is the
//! blue channel, the next byte is the green channel, and the third byte is the
//! red channel.
//!
//! This function translates a 24-bit RGB color into a value that can be
//! written into the display's frame buffer in order to reproduce that color,
//! or the closest possible approximation of that color.
//!
//! \return Returns the display-driver specific color.
//
//*****************************************************************************
static unsigned long
GrOffScreen4BPPColorTranslate(void *pvDisplayData, unsigned long ulValue)
{
    unsigned long ulIdx, ulDiff, ulMatchIdx, ulMatchDiff, ulR, ulG, ulB;
    unsigned char *pucPalette;

    //
    // Check the arguments.
    //
    ASSERT(pvDisplayData);

    //
    // Get a pointer to the palette for the off-screen buffer.
    //
    pucPalette = (unsigned char *)pvDisplayData + 6;

    //
    // Extract the red, green, and blue component from the input color.
    //
    ulR = (ulValue >> ClrRedShift) & 0xff;
    ulG = (ulValue >> ClrGreenShift) & 0xff;
    ulB = (ulValue >> ClrBlueShift) & 0xff;

    //
    // Set the match such that the first palette entry will be a better match.
    //
    ulMatchIdx = 0;
    ulMatchDiff = 0xffffffff;

    //
    // Loop through the colors in the palette.
    //
    for(ulIdx = 0; ulIdx < 16; ulIdx++, pucPalette += 3)
    {
        //
        // Compute the Cartesian distance between these two colors.
        //
        ulDiff = (((pucPalette[2] - ulR) * (pucPalette[2] - ulR)) +
                  ((pucPalette[1] - ulG) * (pucPalette[1] - ulG)) +
                  ((pucPalette[0] - ulB) * (pucPalette[0] - ulB)));

        //
        // See if this color is a closer match than any of the previous colors.
        //
        if(ulDiff < ulMatchDiff)
        {
            //
            // Save this color as the new best match.
            //
            ulMatchDiff = ulDiff;
            ulMatchIdx = ulIdx;
        }

        //
        // Stop looking if an exact match was found.
        //
        if(ulDiff == 0)
        {
            break;
        }
    }

    //
    // Return the index of the best match.
    //
    return(ulMatchIdx);
}

//*****************************************************************************
//
//! Draws a pixel on the screen.
//!
//! \param pvDisplayData is a pointer to the driver-specific data for this
//! display driver.
//! \param lX is the X coordinate of the pixel.
//! \param lY is the Y coordinate of the pixel.
//! \param ulValue is the color of the pixel.
//!
//! This function sets the given pixel to a particular color.  The coordinates
//! of the pixel are assumed to be within the extents of the display.
//!
//! \return None.
//
//*****************************************************************************
static void
GrOffScreen4BPPPixelDraw(void *pvDisplayData, long lX, long lY,
                         unsigned long ulValue)
{
    unsigned char *pucData;
    long lBytesPerRow;

    //
    // Check the arguments.
    //
    ASSERT(pvDisplayData);

    //
    // Create a character pointer for the display-specific data (which points
    // to the image buffer).
    //
    pucData = (unsigned char *)pvDisplayData;

    //
    // Compute the number of bytes per row in the image buffer.
    //
    lBytesPerRow = (*(unsigned short *)(pucData + 1) + 1) / 2;

    //
    // Get the offset to the byte of the image buffer that contains the pixel
    // in question.
    //
    pucData += (lBytesPerRow * lY) + (lX / 2) + 6 + (16 * 3);

    //
    // Determine how much to shift to get to the nibble that contains this
    // pixel.
    //
    lX = (1 - (lX & 1)) * 4;

    //
    // Write this pixel into the image buffer.
    //
    *pucData = (*pucData & ~(0xf << lX)) | (ulValue << lX);
}

//*****************************************************************************
//
//! Draws a horizontal sequence of pixels on the screen.
//!
//! \param pvDisplayData is a pointer to the driver-specific data for this
//! display driver.
//! \param lX is the X coordinate of the first pixel.
//! \param lY is the Y coordinate of the first pixel.
//! \param lX0 is sub-pixel offset within the pixel data, which is valid for 1
//! or 4 bit per pixel formats.
//! \param lCount is the number of pixels to draw.
//! \param lBPP is the number of bits per pixel; must be 1, 4, or 8.
//! \param pucData is a pointer to the pixel data.  For 1 and 4 bit per pixel
//! formats, the most significant bit(s) represent the left-most pixel.
//! \param pucPalette is a pointer to the palette used to draw the pixels.
//!
//! This function draws a horizontal sequence of pixels on the screen, using
//! the supplied palette.  For 1 bit per pixel format, the palette contains
//! pre-translated colors; for 4 and 8 bit per pixel formats, the palette
//! contains 24-bit RGB values that must be translated before being written to
//! the display.
//!
//! \return None.
//
//*****************************************************************************
static void
GrOffScreen4BPPPixelDrawMultiple(void *pvDisplayData, long lX, long lY,
                                 long lX0, long lCount, long lBPP,
                                 const unsigned char *pucData,
                                 const unsigned char *pucPalette)
{
    unsigned char *pucPtr;
    unsigned long ulByte;
    long lBytesPerRow;

    //
    // Check the arguments.
    //
    ASSERT(pvDisplayData);
    ASSERT(pucData);
    ASSERT(pucPalette);

    //
    // Create a character pointer for the display-specific data (which points
    // to the image buffer).
    //
    pucPtr = (unsigned char *)pvDisplayData;

    //
    // Compute the number of bytes per row in the image buffer.
    //
    lBytesPerRow = (*(unsigned short *)(pucPtr + 1) + 1) / 2;

    //
    // Get the offset to the byte of the image buffer that contains the
    // starting pixel.
    //
    pucPtr += (lBytesPerRow * lY) + (lX / 2) + 6 + (16 * 3);

    //
    // Determine how much to shift to get to the nibble that contains this
    // pixel.
    //
    lX = (1 - (lX & 1)) * 4;

    //
    // Determine how to interpret the pixel data based on the number of bits
    // per pixel.
    //
    switch(lBPP)
    {
        //
        // The pixel data is in 1 bit per pixel format.
        //
        case 1:
        {
            //
            // Loop while there are more pixels to draw.
            //
            while(lCount)
            {
                //
                // Get the next byte of image data.
                //
                ulByte = *pucData++;

                //
                // Loop through the pixels in this byte of image data.
                //
                for(; (lX0 < 8) && lCount; lX0++, lCount--)
                {
                    //
                    // Draw this pixel in the appropriate color.
                    //
                    *pucPtr = ((*pucPtr & ~(0xf << lX)) |
                               (((unsigned long *)pucPalette)[(ulByte >>
                                                               (7 - lX0)) &
                                                              1] << lX));
                    if(lX ^= 4)
                    {
                        pucPtr++;
                    }
                }

                //
                // Start at the beginning of the next byte of image data.
                //
                lX0 = 0;
            }

            //
            // The image data has been drawn.
            //
            break;
        }

        //
        // The pixel data is in 4 bit per pixel format.
        //
        case 4:
        {
            //
            // Loop while there are more pixels to draw.  "Duff's device" is
            // used to jump into the middle of the loop if the first nibble of
            // the pixel data should not be used.  Duff's device makes use of
            // the fact that a case statement is legal anywhere within a
            // sub-block of a switch statement.  See
            // http://en.wikipedia.org/wiki/Duff's_device for detailed
            // information about Duff's device.
            //
            switch(lX0 & 1)
            {
                case 0:
                    while(lCount)
                    {
                        //
                        // Get the upper nibble of the next byte of pixel data
                        // and extract the corresponding entry from the
                        // palette.
                        //
                        ulByte = (*pucData >> 4) * 3;
                        ulByte = (*(unsigned long *)(pucPalette + ulByte) &
                                  0x00ffffff);

                        //
                        // Translate this palette entry.
                        //
                        ulByte = GrOffScreen4BPPColorTranslate(pvDisplayData,
                                                               ulByte);

                        //