Implement Grayscale image compression & decompression

homework/grayscale-image/compression.cpp

@@ -0,0 +1,44 @@
+#include "compression.hpp"
+
+std::vector<std::pair<uint8_t, uint8_t>> compressGrayscale(std::array<std::array<uint8_t, width>, height>& bitmap) {
+    std::vector<std::pair<uint8_t, uint8_t>> compressed;
+    for (int i = 0; i < height; i++) {
+        int count = 1, left = bitmap[i][0], right;
+        for (int j = 1; j < width; j++) {
+            right = bitmap[i][j];
+            if (right == left) {
+                count++;
+            } else {
+                compressed.push_back(std::make_pair(left, count));
+                left = right;
+                count = 1;
+            }
+        }
+        compressed.push_back(std::make_pair(left, count));  // push last pixel / series of pixels
+    }
+    return compressed;
+}
+
+std::array<std::array<uint8_t, width>, height> decompressGrayscale(const std::vector<std::pair<uint8_t, uint8_t>>& compressed_bitmap) {
+    std::array<std::array<uint8_t, width>, height> decompressed;
+    int row = 0, column = 0;
+    for (const auto& [value, count] : compressed_bitmap) {
+        std::fill_n(decompressed[row].begin() + column, count, value);
+        column += count;
+        if (column == width) {
+            column = 0;
+            row++;
+        }
+    }
+    // printMap(decompressed);
+    return decompressed;
+}
+
+void printMap(const std::array<std::array<uint8_t, width>, height>& bitmap) {
+    for (int i = 0; i < height; i++) {
+        for (int j = 0; j < width; j++) {
+            std::cout << std::setw(3) << int(bitmap[i][j]) << ' ';
+        }
+        std::cout << "\n";
+    }
+}

homework/grayscale-image/compression.hpp

@@ -0,0 +1,15 @@
+#pragma once
+#include <algorithm>
+#include <array>
+#include <cstdint>
+#include <iomanip>
+#include <iostream>
+#include <utility>
+#include <vector>
+
+constexpr size_t width = 240;
+constexpr size_t height = 160;
+
+std::vector<std::pair<uint8_t, uint8_t>> compressGrayscale(std::array<std::array<uint8_t, width>, height>& bitmap);
+std::array<std::array<uint8_t, width>, height> decompressGrayscale(const std::vector<std::pair<uint8_t, uint8_t>>& compressed_bitmap);
+void printMap(const std::array<std::array<uint8_t, width>, height>& bitmap);

homework/grayscale-image/main.cpp

@@ -1,7 +1,7 @@
 #include <array>
 #include <forward_list>
 
-// TODO: include
+#include "compression.hpp"
 
 std::array<std::array<uint8_t, 32>, 32> generateNinja() {
     return {
@@ -41,10 +41,10 @@ std::array<std::array<uint8_t, 32>, 32> generateNinja() {
 }
 
 int main() {
-    auto ninja = generateNinja();
+    // auto ninja = generateNinja();
     // printMap(ninja);
-    auto compressed = compressGrayscale(ninja);
-    auto decompressed = decompressGrayscale(compressed);
+    // auto compressed = compressGrayscale(ninja);
+    // auto decompressed = decompressGrayscale(compressed);
     // printMap(decompressed);
 
     return 0;

homework/grayscale-image/test.cpp

@@ -4,6 +4,7 @@
 #include <vector>
 
 // TODO: include
+#include "compression.hpp"
 #include "gtest/gtest.h"
 
 void expectBitmap(const std::vector<std::pair<uint8_t, uint8_t>>& bitmap, size_t fraction) {