feat: add ImageDataDecoder — LSB steganography decoder

Reads hidden messages from encoded PNG images by extracting
LSB data from channels indicated by the pixel 0 header.

ImageDataDecoder/ImageDataDecoder.cpp

@@ -0,0 +1,98 @@
+#define _CRT_SECURE_NO_WARNINGS
+#include <iostream>
+#include <string>
+#include <stdexcept>
+#include <cstdlib>
+
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+int width, height, channels;
+std::string inputPath, message;
+bool useR, useG, useB;
+unsigned char* data;
+
+void loadImage() {
+    data = stbi_load(inputPath.c_str(), &width, &height, &channels, 0);
+    if (!data) {
+        throw std::runtime_error("Failed to load image: " + inputPath);
+    }
+
+    if (channels < 3) {
+        stbi_image_free(data);
+        throw std::runtime_error("Image must have at least 3 channels (RGB). Found: " + std::to_string(channels));
+    }
+}
+
+void getInputPath() {
+    std::cout << "Enter image file path: ";
+    std::getline(std::cin, inputPath);
+    if (inputPath.size() >= 2 && inputPath.front() == '"' && inputPath.back() == '"') {
+        inputPath = inputPath.substr(1, inputPath.size() - 2);
+    }
+}
+
+void readChannelHeaders() {
+    useR = data[0] & 1;
+    useG = data[1] & 1;
+    useB = data[2] & 1;
+
+    if (!useR && !useG && !useB) {
+        stbi_image_free(data);
+        throw std::runtime_error("No active channels found in header pixel. Image may not contain a hidden message.");
+    }
+
+    std::cout << "Active channels: " << (useR ? "R" : "") << (useG ? "G" : "") << (useB ? "B" : "") << "\n";
+}
+
+bool processBit(int channelOffset, int base, unsigned char& currentByte, int& bitCount) {
+    int bit = data[base + channelOffset] & 1;
+    currentByte = (currentByte << 1) | bit;
+    bitCount++;
+    if (bitCount == 8) {
+        if (currentByte == '\0') return true; // null terminator found
+        message.push_back(static_cast<char>(currentByte));
+        currentByte = 0;
+        bitCount = 0;
+    }
+    return false;
+}
+
+void readMessage() {
+    int totalPixels = width * height;
+    unsigned char currentByte = 0;
+    int bitCount = 0;
+
+    for (int pixel = 1; pixel < totalPixels; pixel++) {
+        int base = pixel * channels;
+
+        if (useR && processBit(0, base, currentByte, bitCount)) return;
+        if (useG && processBit(1, base, currentByte, bitCount)) return;
+        if (useB && processBit(2, base, currentByte, bitCount)) return;
+    }
+}
+
+int main() {
+    try {
+        getInputPath();
+        loadImage();
+        readChannelHeaders();
+        readMessage();
+
+        stbi_image_free(data);
+
+        if (message.empty()) {
+            std::cout << "No message found (or message is empty).\n";
+        } else {
+            std::cout << "Hidden message (" << message.size() << " bytes):\n";
+            std::cout << message << "\n";
+        }
+
+    } catch (const std::exception& e) {
+        std::cerr << "Error: " << e.what() << "\n";
+        std::cin.get();
+        return EXIT_FAILURE;
+    }
+    std::cin.get();
+    return EXIT_SUCCESS;
+}

ImageDataDecoder/ImageDataDecoder.vcxproj

@@ -0,0 +1,138 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <VCProjectVersion>18.0</VCProjectVersion>
+    <Keyword>Win32Proj</Keyword>
+    <ProjectGuid>{b2c3d4e5-f6a7-8901-bcde-f12345678901}</ProjectGuid>
+    <RootNamespace>ImageDataDecoder</RootNamespace>
+    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <PlatformToolset>v145</PlatformToolset>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <PlatformToolset>v145</PlatformToolset>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <PlatformToolset>v145</PlatformToolset>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <PlatformToolset>v145</PlatformToolset>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="Shared">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets" Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <ClCompile>
+      <WarningLevel>Level3</WarningLevel>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>WIN32;_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
+    <ClCompile>
+      <WarningLevel>Level3</WarningLevel>
+      <FunctionLevelLinking>true</FunctionLevelLinking>
+      <IntrinsicFunctions>true</IntrinsicFunctions>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>WIN32;NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
+    <ClCompile>
+      <WarningLevel>Level3</WarningLevel>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
+    <ClCompile>
+      <WarningLevel>Level3</WarningLevel>
+      <FunctionLevelLinking>true</FunctionLevelLinking>
+      <IntrinsicFunctions>true</IntrinsicFunctions>
+      <SDLCheck>true</SDLCheck>
+      <PreprocessorDefinitions>NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <ConformanceMode>true</ConformanceMode>
+      <LanguageStandard>stdcpp20</LanguageStandard>
+    </ClCompile>
+    <Link>
+      <SubSystem>Console</SubSystem>
+      <GenerateDebugInformation>true</GenerateDebugInformation>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <ClCompile Include="ImageDataDecoder.cpp" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="stb_image.h" />
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>