src/base/pixel.hh

/*
 * Copyright (c) 2015 ARM Limited
 * All rights reserved
 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
 * unmodified and in its entirety in all distributions of the software,
 * modified or unmodified, in source code or in binary form.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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 */

#ifndef __BASE_PIXEL_HH__
#define __BASE_PIXEL_HH__

#include <cmath>
#include <cstdint>
#include <string>
#include <vector>

#include "base/compiler.hh"
#include "base/cprintf.hh"
#include "base/str.hh"
#include "base/types.hh"
#include "sim/byteswap.hh"

namespace gem5
{

/**
 * Internal gem5 representation of a Pixel.
 */
struct Pixel
{
    Pixel()
        : red(0), green(0), blue(0), padding(0) {}

    Pixel(uint8_t _red, uint8_t _green, uint8_t _blue)
        : red(_red), green(_green), blue(_blue), padding(0) {}

    uint8_t red;
    uint8_t green;
    uint8_t blue;
    uint8_t padding;
};

inline bool
operator==(const Pixel &lhs, const Pixel &rhs)
{
    return lhs.red == rhs.red &&
        lhs.green == rhs.green &&
        lhs.blue == rhs.blue &&
        lhs.padding == rhs.padding;
}

/**
 * Configurable RGB pixel converter.
 *
 * This class converts between external RGB representations and gem5's
 * internal Pixel representation. The class assumes that pixels are
 * stored in a word of configurable length (up to 32 bits). Individual
 * pixels are assumed to be represented by contiguous bit ranges in
 * the word (i.e., it is possible to shift and mask out a contiguous
 * bit range for each pixel).
 */
class PixelConverter
{
  public:
    /**
     * Color channel conversion and scaling helper class.
     */
    struct Channel
    {
        /**
         * @param offset Offset in bits.
         * @param width Width in bits.
         */
        Channel(unsigned offset, unsigned width);

        /**
         * Get the value of a single color channel represented as an
         * 8-bit number.
         */
        uint8_t toPixel(uint32_t word) const {
            return round(((word >> offset) & mask) * factor);
        }

        /**
         * Convert an 8-bit representation of a color into an external
         * format.
         */
        uint32_t fromPixel(uint8_t ch) const {
            return (static_cast<uint8_t>(round(ch / factor)) & mask) << offset;
        }

        /** Offset in bits */
        unsigned offset;
        /** Bit mask (after shifting) */
        unsigned mask;
        /**
         * Scaling factor when converting to the full range of an
         * 8-bit color channel
         */
        float factor;
    };

    PixelConverter(unsigned length,
                   unsigned ro, unsigned go, unsigned bo,
                   unsigned rw, unsigned gw, unsigned bw,
                   ByteOrder byte_order = ByteOrder::little);

    /** Get the Pixel representation of a color word. */
    Pixel toPixel(uint32_t word) const {
        return Pixel(ch_r.toPixel(word),
                     ch_g.toPixel(word),
                     ch_b.toPixel(word));
    }

    /** Get a Pixel representation by reading a word from memory. */
    Pixel toPixel(const uint8_t *rfb) const {
        return toPixel(readWord(rfb));
    }

    /** Convert a Pixel into a color word */
    uint32_t fromPixel(const Pixel &pixel) const {
        return ch_r.fromPixel(pixel.red) |
            ch_g.fromPixel(pixel.green) |
            ch_b.fromPixel(pixel.blue);
    }

    /**
     * Convert a pixel into a color word and store the resulting word
     * in memory.
     */
    void fromPixel(uint8_t *rfb, const Pixel &pixel) const {
        writeWord(rfb, fromPixel(pixel));
    }

    /**
     * Read a word of a given length and endianness from memory.
     *
     * The number of bytes read from memory is determined by the
     * length of a color word. Note that some of the bytes may be
     * padding.
     *
     * @param p Pointer to the first byte in the word.
     * @return Word in host endianness.
     */
    uint32_t readWord(const uint8_t *p) const;
    /**
     * Write a word of a given length and endianness to memory.
     *
     * @param p Pointer to the first byte in memory.
     * @param word Word to store (host endianness).
     */
    void writeWord(uint8_t *p, uint32_t word) const;

    /** Bytes per pixel when stored in memory (including padding) */
    unsigned length;
    /**
     * Number of bits used to represent one pixel value (excluding
     * padding). This could be less than length * 8 if the pixel value
     * is padded.
     */
    unsigned depth;
    /** Byte order when stored to memory. */
    ByteOrder byte_order;

    /** Red channel conversion helper */
    Channel ch_r;
    /** Green channel conversion helper */
    Channel ch_g;
    /** Blue channel conversion helper */
    Channel ch_b;

    /** Predefined 32-bit RGB (red in least significant bits, 8
     * bits/channel, little endian) conversion helper */
    static const PixelConverter rgba8888_le;
    /** Predefined 16-bit RGB565 (red in least significant bits,
     * little endian) conversion helper */
    static const PixelConverter rgb565_le;

    /** Predefined 32-bit RGB (red in least significant bits, 8
     * bits/channel, big endian) conversion helper */
    static const PixelConverter rgba8888_be;
    /** Predefined 16-bit RGB565 (red in least significant bits,
     * big endian) conversion helper */
    static const PixelConverter rgb565_be;
};

inline bool
to_number(const std::string &value, Pixel &retval)
{
    uint32_t num;
    if (!to_number(value, num))
        return false;

    retval = PixelConverter::rgba8888_le.toPixel(num);
    return true;
}

inline std::ostream &
operator<<(std::ostream &os, const Pixel &pxl)
{
    os << csprintf("%#.08x", PixelConverter::rgba8888_le.fromPixel(pxl));
    return os;
}

} // namespace gem5

#endif // __BASE_PIXEL_HH__