Простейшее чтение BMP-файла. Логика вынесена в класс.

CMakeLists.txt

@@ -3,4 +3,6 @@ project(image_test_cpp)
 
 set(CMAKE_CXX_STANDARD 17)
 
-add_executable(image_test_cpp main.cpp)
+add_executable(image_test_cpp main.cpp
+        bmpimage.h
+        bmpimage.cpp)

bmpimage.cpp

@@ -0,0 +1,68 @@
+#include "bmpimage.h"
+
+BMPImage::BMPImage(BitmapFileHeader &fileHeader, BITMAPINFOHEADER &infoHeader, Pixel **pixelArray) {
+    this->fileHeader = fileHeader;
+    this->infoHeader = infoHeader;
+    this->pixelArray = pixelArray;
+}
+
+const uint32_t &BMPImage::width() const { return this->infoHeader.BitmapWidth; }
+
+const uint32_t &BMPImage::height() const { return this->infoHeader.BitmapHeight; }
+
+void BMPImage::write(const std::string &filename) {
+    {
+        std::ofstream ofs(filename, std::ios_base::binary);
+        ofs.write((char *) &this->fileHeader, sizeof(this->fileHeader));
+        ofs.write((char *) &this->infoHeader, sizeof(this->infoHeader));
+        uint32_t byteByRow = this->infoHeader.BitmapWidth * 3;
+        uint8_t padding = 4 - this->infoHeader.BitmapWidth % 4;
+        for (int i = 0; i < this->infoHeader.BitmapHeight; ++i) {
+            ofs.write((char *) pixelArray[i], byteByRow);
+            if (padding != 4) ofs.write(PADDING_ZEROES, padding); // Write padding
+        }
+    }
+}
+
+BMPImage readBMPImage(const std::string &filename) {
+    BitmapFileHeader bitmapFileHeader;
+    BITMAPINFOHEADER bitmapInfoHeader;
+    Pixel **pixelArray;
+    uint32_t DIB_Header_Size;
+    {
+        std::ifstream ifs(filename, std::ios_base::binary);
+        if (!ifs.good()) {
+            throw std::runtime_error("File read error");
+        }
+        ifs.seekg(0, std::ios::beg);
+        ifs.read((char *) &bitmapFileHeader, sizeof(bitmapFileHeader));
+        ifs.read((char *) &DIB_Header_Size, sizeof(DIB_Header_Size));
+    }
+    if (DIB_Header_Size != 40) {
+        throw std::runtime_error("Invalid header");
+    }
+    {
+        std::ifstream ifs(filename, std::ios_base::binary);
+        if (!ifs.good()) {
+            throw std::runtime_error("File read error");
+        }
+        ifs.seekg(14, std::ios::beg);
+        ifs.read((char *) &bitmapInfoHeader, sizeof(bitmapInfoHeader));
+    }
+    pixelArray = new Pixel *[bitmapInfoHeader.BitmapHeight];
+    {
+        std::ifstream ifs(filename, std::ios_base::binary);
+        if (!ifs.good()) {
+            throw std::runtime_error("File read error");
+        }
+        ifs.seekg(bitmapFileHeader.imageDataOffset, std::ios::beg);
+        uint32_t byteByRow = bitmapInfoHeader.BitmapWidth * 3;
+        uint8_t padding = 4 - bitmapInfoHeader.BitmapWidth % 4;
+        for (int i = 0; i < bitmapInfoHeader.BitmapHeight; ++i) {
+            pixelArray[i] = new Pixel[bitmapInfoHeader.BitmapWidth];
+            ifs.read((char *) pixelArray[i], byteByRow);
+            if (padding != 4) ifs.seekg(padding, std::ios_base::cur); // Skip padding
+        }
+    }
+    return {bitmapFileHeader, bitmapInfoHeader, pixelArray};
+}

bmpimage.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <fstream>
+
+const char PADDING_ZEROES[3] = {0, 0, 0};
+
+#pragma pack(push, 1)
+struct BitmapFileHeader {
+    char signature[2] = {0, 0};
+    uint32_t fileSize = 0;
+    uint16_t reserved1 = 0;
+    uint16_t reserved2 = 0;
+    uint32_t imageDataOffset = 0;
+};
+#pragma pack(pop)
+
+#pragma pack(push, 1)
+struct BITMAPINFOHEADER {
+    uint32_t HeaderSize = 0;
+    uint32_t BitmapWidth = 0;
+    uint32_t BitmapHeight = 0;
+    uint16_t ColorPlanes = 0;
+    uint16_t BitsPerPixel = 0;
+    uint32_t CompressionMethod = 0;
+    uint32_t ImageSize = 0;
+    int32_t HorizontalPixelPerMetre = 0;
+    int32_t VerticalPixelPerMetre = 0;
+    uint32_t NumberOfColors = 0;
+    uint32_t NumberOfImportantColors = 0;
+};
+#pragma pack(pop)
+
+#pragma pack(push, 1)
+struct Pixel {
+    uint8_t r = 0;
+    uint8_t g = 0;
+    uint8_t b = 0;
+};
+#pragma pack(pop)
+
+class BMPImage {
+    BitmapFileHeader fileHeader;
+    BITMAPINFOHEADER infoHeader;
+    Pixel **pixelArray;
+public:
+    BMPImage(BitmapFileHeader &fileHeader, BITMAPINFOHEADER &infoHeader, Pixel **pixelArray);
+
+    [[nodiscard]] const uint32_t &width() const;
+
+    [[nodiscard]] const uint32_t &height() const;
+
+    void write(const std::string &);
+};
+
+BMPImage readBMPImage(const std::string &filename);

main.cpp

@@ -1,27 +1,12 @@
 #include <iostream>
-#include <cstdint>
-#include <filesystem>
-#include <fstream>
+#include "bmpimage.h"
 
-struct BitmapFileHeader {
-    char signature[2] = {0, 0};
-    uint32_t fileSize = 0;
-    uint16_t reserved1 = 0;
-    uint16_t reserved2 = 0;
-    uint32_t imageDataOffset = 0;
-};
+const std::string FILENAME = "../elef.bmp";
+const std::string FILENAME_OUT = "../elef_out.bmp";
 
-const std::string FILENAME = "elef.bmp";
 
 int main() {
-    BitmapFileHeader bitmapFileHeader;
-    {
-        std::ifstream ifs(FILENAME, std::ios_base::binary);
-        ifs.seekg(0, std::ios::beg);
-        ifs.read((char *) &bitmapFileHeader, 14);
-    }
-    std::cout << "Structure:\n" << "Signature: " << std::string(bitmapFileHeader.signature, 2) << "\nFile size: "
-              << bitmapFileHeader.fileSize << "\nReserved 1: " << bitmapFileHeader.reserved1 << "\nReserved 2: "
-              << bitmapFileHeader.reserved2 << "\nImage data offset: " << bitmapFileHeader.imageDataOffset << std::endl;
+    auto image = readBMPImage(FILENAME);
+    image.write(FILENAME_OUT);
     return 0;
 }