Added Read method

.gitignore

@@ -1,6 +1,12 @@
 # Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
 # Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
 
+# All images
+*.bmp
+*.jpg
+*.jpeg
+*.png
+
 # Vim swap files
 *.swp
 

Exec/CMakeLists.txt

@@ -4,6 +4,7 @@ project(BmpPP_exec)
 set(CMAKE_CXX_STANDARD 17)
 
 ADD_COMPILE_DEFINITIONS(_EULE_NO_INTRINSICS_)
+ADD_COMPILE_DEFINITIONS(_BMPLIB_DEBUG_OUTPUT_)
 
 INCLUDE_DIRECTORIES(../Src/Eule/)
 INCLUDE_DIRECTORIES(../Src/)

Exec/main.cpp

@@ -6,6 +6,7 @@ using namespace Leonetienne::BmpPP;
 
 int main() {
 
+    /*
     BMP bmp({800, 600}, Colormode::RGB);
 
     for (int x = 0; x < 800; x++)
@@ -19,8 +20,19 @@ int main() {
         );
     }
 
-    if (!bmp.Write("test.bmp"))
-        std::cerr << "What the hell" << std::endl;
+    */
+
+    BMP bmp;
+
+    if (!bmp.Read("test.bmp"))
+        std::cerr << "Failed to read" << std::endl;
+
+    std::cout << (bmp.GetColormode() == Colormode::RGB) << std::endl;
+
+    if (!bmp.Write("testwrite.bmp"))
+       std::cerr << "What the hell" << std::endl;
+
+
 
     return 0;
 }

Src/BMP.cpp

@@ -1,8 +1,7 @@
 #include "BMP.h"
-#include <iostream>
-#include <fstream>
 #include <stdexcept>
 #include "BmpWriter.h"
+#include "BmpReader.h"
 
 #define CHECK_IF_INITIALIZED if (!isInitialized) throw std::runtime_error("Image not initialized!");
 
@@ -13,6 +12,14 @@ namespace Leonetienne::BmpPP {
         return;
     }
 
+
+    BMP::BMP(const std::string &filename) {
+        if(!Read(filename))
+            throw std::runtime_error("Unable to read bmp image!");
+
+        return;
+    }
+
     BMP::BMP(const Eule::Vector2i &size, const Colormode& colormode)
         :
         size { size },
@@ -57,17 +64,7 @@ namespace Leonetienne::BmpPP {
     }
 
     bool BMP::Read(const std::string &filename) {
-
-        std::ifstream ifs(filename, std::ifstream::binary);
-        if (!ifs.good())
-            return false;
-
-        // When reading the image, we don't care about most of the header.
-        // All we want is the images resolutions, bits-per-pixel, and pixelbuffer address...
-        // This is because we do not support ALL of bmp, but just the most common formats...
-
-
-        return true;
+        return BmpReader::Read(*this, filename);
     }
 
     std::uint8_t *BMP::GetPixel(const Eule::Vector2i &position) {

Src/BMP.h

@@ -9,12 +9,19 @@
 namespace Leonetienne::BmpPP {
 
     class BmpWriter;
+    class BmpReader;
 
     class BMP {
     public:
+        // Will create an uninitialized image
         BMP();
+
+        //! Will create an image with the entire pixel buffer set to 0
         explicit BMP(const Eule::Vector2i& size, const Colormode& colormode = Colormode::RGBA);
 
+        //! Will create a image and read it from a bmp file
+        explicit BMP(const std::string& filename);
+
         //! Will return a pointer to the first byte of a pixel at a given position
         std::uint8_t* GetPixel(const Eule::Vector2i& position);
 
@@ -66,6 +73,7 @@ namespace Leonetienne::BmpPP {
         bool isInitialized = false;
 
         friend class BmpWriter;
+        friend class BmpReader;
     };
 
 }

Src/BmpReader.cpp

@@ -0,0 +1,199 @@
+#include "BmpReader.h"
+#include "Colormodes.h"
+#include "BMP.h"
+#include <fstream>
+#include <cstdint>
+
+#ifdef _BMPLIB_DEBUG_OUTPUT_
+#include <iostream>
+#endif
+
+namespace Leonetienne::BmpPP {
+
+    bool BmpReader::Read(BMP &image, const std::string &filename) {
+        // Open file
+        std::ifstream ifs(filename, std::ifstream::binary);
+        if (!ifs.good())
+            return false;
+
+        // When reading the image, we don't care about most of the header.
+        // All we want is the images resolution, bits-per-pixel, and the pixelbuffer address...
+        // This is because we do not support ALL of bmp, but just the most common formats...
+
+        // Fetch bmp signature
+        std::uint16_t signature;
+        ReadBytes(ifs, signature);
+
+        // Does the signature match?
+        if (signature != 0x4D42) {
+            #ifdef _BMPLIB_DEBUG_OUTPUT_
+            std::cerr << "Bmp signature doesn't match" << std::endl;
+            #endif
+            ifs.close();
+            return false;
+        }
+
+        // Skip eight useless bytes (filesize + reserved0 + reserved1)
+        ifs.ignore(8);
+
+        // Read the address of the pixel buffer
+        std::uint32_t pixelBufferAddress;
+        ReadBytes(ifs, pixelBufferAddress);
+
+        // Read the size of the dib header
+        std::uint32_t dibHeaderSize;
+        ReadBytes(ifs, dibHeaderSize);
+
+        std::uint32_t width;
+        std::uint32_t height;
+        std::uint16_t bitsPerPixel;
+
+        // Check if what kind of dib header we're dealing with
+        // These are the two we're supporting (to read, at least).
+        if (dibHeaderSize == 12) {
+            // BITMAPCOREHEADER it is
+
+            // Read the width and the height (both 2-byte ints)
+            std::uint16_t width_2byte;
+            std::uint16_t height_2byte;
+
+            ifs >> width_2byte;
+            ifs >> height_2byte;
+            ReadBytes(ifs, width_2byte);
+            ReadBytes(ifs, height_2byte);
+
+            width = width_2byte;
+            height = height_2byte;
+
+            // Read the bits per pixel
+            ReadBytes(ifs, bitsPerPixel);
+        }
+        else if (dibHeaderSize == 40) {
+            // BITMAPINFOHEADER it is
+
+            // Read the width and height (both 4-byte signed ints)
+            std::int32_t width_4byte_signed;
+            std::int32_t height_4byte_signed;
+
+            ReadBytes(ifs, width_4byte_signed);
+            ReadBytes(ifs, height_4byte_signed);
+
+            width = width_4byte_signed;
+            height = height_4byte_signed;
+
+            // Skip two useless bytes
+            ifs.ignore(2);
+
+            // Read the bits per pixel value
+            ReadBytes(ifs, bitsPerPixel);
+        }
+        else if (dibHeaderSize == 124) {
+            // BITMAPV5HEADER it is
+
+            // Read the width and height
+            ReadBytes(ifs, width);
+            ReadBytes(ifs, height);
+
+            // Skip two useless bytes
+            ifs.ignore(2);
+
+            // Read the bits per pixel value
+            ReadBytes(ifs, bitsPerPixel);
+        }
+        else {
+            #ifdef _BMPLIB_DEBUG_OUTPUT_
+            std::cerr << "Unsupported dib header found. Dib header size: " << dibHeaderSize << " bytes." << std::endl;
+            #endif
+            ifs.close();
+            return false;
+        }
+
+        // Convert bits per pixel to color mode
+        Colormode colormode;
+        switch (bitsPerPixel) {
+            case 32:
+                colormode = Colormode::RGBA;
+                break;
+
+            case 24:
+                colormode = Colormode::RGB;
+                break;
+
+            default:
+                #ifdef _BMPLIB_DEBUG_OUTPUT_
+                std::cerr << "Unsupported pixel format found (bits per pixel). Bits per pixel: " << bitsPerPixel << std::endl;
+                #endif
+                ifs.close();
+                return false;
+        }
+
+        // Now read the pixel array
+        // Pre-calculate the channel count
+        const std::size_t numChannels = bitsPerPixel / 8;
+
+        // Calculate how much padding there should be between each row
+        const std::size_t paddingBytesPerRow = (4 - ((width * numChannels) % 4)) % 4;
+
+        // Calculate how long bytes we should care about per row (so, excluding padding)
+        const std::size_t rowWidth = width * numChannels;
+
+        // Create the pixel buffer
+        std::vector<std::uint8_t> pixelArray;
+        pixelArray.resize(width * height * numChannels);
+
+        // Set the reading-head to the address of the pixel array
+        ifs.seekg(pixelBufferAddress);
+
+        // Iterate over all rows, and skip padding after each row
+        for (std::int64_t y = height-1; y >= 0; y--) {
+            const std::size_t rowIndex = y * width * numChannels;
+
+            for (std::size_t x = 0; x < width; x++) {
+                const std::size_t pixelIndex = rowIndex + x * numChannels;
+
+                switch (colormode) {
+                    case Colormode::RGBA: {
+                        std::uint8_t r, g, b, a;
+                        ReadBytes(ifs, b);
+                        ReadBytes(ifs, g);
+                        ReadBytes(ifs, r);
+                        ReadBytes(ifs, a);
+
+                        pixelArray[pixelIndex + 0] = r;
+                        pixelArray[pixelIndex + 1] = g;
+                        pixelArray[pixelIndex + 2] = b;
+                        pixelArray[pixelIndex + 3] = a;
+                    }
+                    break;
+
+                    case Colormode::RGB: {
+                        std::uint8_t r, g, b;
+                        ReadBytes(ifs, b);
+                        ReadBytes(ifs, g);
+                        ReadBytes(ifs, r);
+
+                        pixelArray[pixelIndex + 0] = r;
+                        pixelArray[pixelIndex + 1] = g;
+                        pixelArray[pixelIndex + 2] = b;
+                    }
+                    break;
+                }
+            }
+
+            if (paddingBytesPerRow > 0)
+                ifs.ignore(paddingBytesPerRow);
+        }
+
+        // We are done with the file
+        ifs.close();
+
+        // Now construct our image
+        image.ReInitialize(Eule::Vector2i(width, height), colormode);
+
+        // We're a friend-class, so we're going to MOVE (not copy) the pixels over manually. Much faster.
+        image.pixelBuffer.swap(pixelArray);
+
+        // Done.
+        return true;
+    }
+}

Src/BmpReader.h

@@ -0,0 +1,36 @@
+#ifndef BMPPP_BMPREADER_H
+#define BMPPP_BMPREADER_H
+
+#include <string>
+#include <fstream>
+
+namespace Leonetienne::BmpPP {
+
+    class BMP;
+
+    class BmpReader {
+    public:
+        static bool Read(BMP& image, const std::string& filename);
+
+    private:
+        // Will read sizeof(T) bytes of is into buffer
+        template <typename T>
+        static std::ifstream& ReadBytes(std::ifstream& is, T& buffer) {
+            const std::size_t sizeofT = sizeof(T);
+            buffer = 0x0;
+            std::uint8_t buf;
+
+            for (std::size_t i = 0; i < sizeofT; i++)
+            {
+                is.read((char*)&buf, 1);
+                T bbuf = buf << (i * 8);
+                buffer |= bbuf;
+            }
+
+            return is;
+        }
+    };
+
+}
+
+#endif //BMPP_BMPREADER_H

Src/BmpWriter.cpp

@@ -33,10 +33,10 @@ namespace Leonetienne::BmpPP {
         const std::size_t numChannels = image.GetNumColorChannels();
 
         // Calculate how many padding bytes to add per row
-        std::size_t paddingBytesPerRow = (4 - ((image.size.x * numChannels) % 4)) % 4;
+        const std::size_t paddingBytesPerRow = (4 - ((image.size.x * numChannels) % 4)) % 4;
 
         // Iterate over all pixel rows
-        for (std::size_t y = 0; y < image.size.y; y++) {
+        for (std::int64_t y = image.size.y-1; y >= 0; y--) {
             const std::size_t rowIndex = y * image.size.x * numChannels;
 
             for (std::size_t x = 0; x < image.size.x; x++) {

Src/CMakeLists.txt

@@ -12,5 +12,6 @@ add_library(BmpPP
 
     BMP.cpp
     BmpWriter.cpp
+    BmpReader.cpp
     BmpHeader.cpp
 )