Add processing of ppm image into color output

src/pixels.cpp

@@ -0,0 +1,26 @@
+#include <memory>
+#include <libscterm.hpp>
+#include <netpbm/pam.h>
+#include "pixels.hpp"
+
+void write_image(std::ostream& os, const std::string& path) {
+    std::unique_ptr<FILE, void(*)(FILE*)> infile {pm_openr(path.c_str()), pm_close};
+    struct pam info;
+    pnm_readpaminit(infile.get(), &info, PAM_STRUCT_SIZE(tuple_type));
+    std::unique_ptr<tuple, void(*)(void*)> row1 {pnm_allocpamrow(&info), pm_freerow};
+    std::unique_ptr<tuple, void(*)(void*)> row2 {pnm_allocpamrow(&info), pm_freerow};
+    for (int y = 0; y < info.height; y += 2) {
+        pnm_readpamrow(&info, row1.get());
+        pnm_readpamrow(&info, row2.get());
+        for (int x = 0; x < info.width; ++x) {
+            if (info.depth == 3) { // assume RGB, 1 byte per sample
+                tuple* t1 {row1.get()};
+                os << sc::io::truecolorb(t1[x][0], t1[x][1], t1[x][2]);
+                tuple* t2 {row2.get()};
+                os << sc::io::truecolorf(t2[x][0], t2[x][1], t2[x][2]);
+                os << u8"\u2584"; // unicode lower half block
+            }
+        }
+        os << sc::io::reset << '\n';
+    }
+}

src/pixels.hpp

@@ -0,0 +1,8 @@
+#ifndef PIXELS_H_
+#define PIXELS_H_
+
+#include <iostream>
+
+void write_image(std::ostream& os, const std::string& path);
+
+#endif // PIXELS_H_