ImageView.h

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/*
* Copyright 2019 Axel Waggershauser
*/
// SPDX-License-Identifier: Apache-2.0
 
#pragma once
 
#include <algorithm>
#include <cstdint>
#include <cstdio>
#include <memory>
#include <stdexcept>
 
namespace ZXing {

enum class ImageFormat : uint32_t
{
    None = 0,
    Lum  = 0x01000000,
    LumA = 0x02000000,
    RGB  = 0x03000102,
    BGR  = 0x03020100,
    RGBA = 0x04000102,
    ARGB = 0x04010203,
    BGRA = 0x04020100,
    ABGR = 0x04030201,
    RGBX [[deprecated("use RGBA")]] = RGBA,
    XRGB [[deprecated("use ARGB")]] = ARGB,
    BGRX [[deprecated("use BGRA")]] = BGRA,
    XBGR [[deprecated("use ABGR")]] = ABGR,
};

constexpr inline int PixStride(ImageFormat format) { return (static_cast<uint32_t>(format) >> 3*8) & 0xFF; }
constexpr inline int RedIndex(ImageFormat format) { return (static_cast<uint32_t>(format) >> 2*8) & 0xFF; }
constexpr inline int GreenIndex(ImageFormat format) { return (static_cast<uint32_t>(format) >> 1*8) & 0xFF; }
constexpr inline int BlueIndex(ImageFormat format) { return (static_cast<uint32_t>(format) >> 0*8) & 0xFF; }
 
constexpr inline uint8_t RGBToLum(unsigned r, unsigned g, unsigned b)
{
    // .299R + 0.587G + 0.114B (YUV/YIQ for PAL and NTSC),
    // (306*R) >> 10 is approximately equal to R*0.299, and so on.
    // 0x200 >> 10 is 0.5, it implements rounding.
    return static_cast<uint8_t>((306 * r + 601 * g + 117 * b + 0x200) >> 10);
}

class ImageView
{
protected:
    const uint8_t* _data = nullptr;
    ImageFormat _format = ImageFormat::None;
    int _width = 0, _height = 0, _pixStride = 0, _rowStride = 0;
 
public:
    ImageView() = default;

    ImageView(const uint8_t* data, int width, int height, ImageFormat format, int rowStride = 0, int pixStride = 0)
        : _data(data),
          _format(format),
          _width(width),
          _height(height),
          _pixStride(pixStride ? pixStride : PixStride(format)),
          _rowStride(rowStride ? rowStride : width * _pixStride)
    {
        // TODO: [[deprecated]] this check is to prevent existing code from suddenly throwing, remove in 3.1
        if (_data == nullptr && _width == 0 && _height == 0 && rowStride == 0 && pixStride == 0) {
            fprintf(stderr, "zxing-cpp deprecation warning: ImageView(nullptr, ...) will throw in the future, use ImageView()\n");
            return;
        }
 
        if (_data == nullptr)
            throw std::invalid_argument("Can not construct an ImageView from a NULL pointer");
 
        if (_width <= 0 || _height <= 0)
            throw std::invalid_argument("Neither width nor height of ImageView can be less or equal to 0");
    }

    ImageView(const uint8_t* data, int size, int width, int height, ImageFormat format, int rowStride = 0, int pixStride = 0)
        : ImageView(data, width, height, format, rowStride, pixStride)
    {
        if (_rowStride < 0 || _pixStride < 0 || size < _height * _rowStride)
            throw std::invalid_argument("ImageView parameters are inconsistent (out of bounds)");
    }
 
    int width() const { return _width; }
    int height() const { return _height; }
    int pixStride() const { return _pixStride; }
    int rowStride() const { return _rowStride; }
    ImageFormat format() const { return _format; }
 
    const uint8_t* data() const { return _data; }
    const uint8_t* data(int x, int y) const { return _data + y * _rowStride + x * _pixStride; }

    ImageView cropped(int left, int top, int width, int height) const
    {
        left   = std::clamp(left, 0, _width - 1);
        top    = std::clamp(top, 0, _height - 1);
        width  = width <= 0 ? (_width - left) : std::min(_width - left, width);
        height = height <= 0 ? (_height - top) : std::min(_height - top, height);
        return {data(left, top), width, height, _format, _rowStride, _pixStride};
    }

    ImageView rotated(int degree) const
    {
        switch ((degree + 360) % 360) {
        case 90:  return {data(0, _height - 1), _height, _width, _format, _pixStride, -_rowStride};
        case 180: return {data(_width - 1, _height - 1), _width, _height, _format, -_rowStride, -_pixStride};
        case 270: return {data(_width - 1, 0), _height, _width, _format, -_pixStride, _rowStride};
        default:  return *this;
        }
    }

    ImageView subsampled(int scale) const
    {
        return {_data, _width / scale, _height / scale, _format, _rowStride * scale, _pixStride * scale};
    }
 
};

class Image : public ImageView
{
    std::unique_ptr<uint8_t[]> _memory;
    Image(std::unique_ptr<uint8_t[]>&& data, int w, int h, ImageFormat f) : ImageView(data.get(), w, h, f), _memory(std::move(data)) {}
 
public:
    Image() = default;
    Image(int w, int h, ImageFormat f = ImageFormat::Lum) : Image(std::make_unique<uint8_t[]>(w * h * PixStride(f)), w, h, f) {}
};
 
} // ZXing