1 files changed, 60 insertions, 0 deletions
diff --git a/libraries/daguerre/source/ppm.cpp b/libraries/daguerre/source/ppm.cpp
new file mode 100644
index 0000000..a4a7e27
--- /dev/null
+++ b/libraries/daguerre/source/ppm.cpp
@@ -0,0 +1,60 @@
+#include <daguerre/ppm.hpp>
+
+namespace daguerre {
+
+  //TODO: make this more robust
+  static unsigned read_text_int(FILE *input) {
+    unsigned n = 0;
+    char ch;
+    fread(&ch, 1, 1, input);
+    if (ch == '#') {
+      do
+        fread(&ch, 1, 1, input);
+      while (ch != '\n');
+      fread(&ch, 1, 1, input);
+    }
+    do {
+      n = n * 10 + ch - '0';
+      fread(&ch, 1, 1, input);
+    } while (ch >= '0' && ch <= '9');
+    return n;
+  }
+
+  //TODO: this only supports p6 format, and assumes max < 256
+  std::optional<image<rgb24>> try_load_ppm(FILE *input) {
+
+    char header[3];
+    if (fread(header, 1, 3, input) != 3)
+      return {};
+
+    if (header[0] != 'P' || header[1] != '6' || header[2] != '\n')
+      return {};
+
+    unsigned width = read_text_int(input);
+    unsigned height = read_text_int(input);
+    unsigned max = read_text_int(input);
+
+    image<rgb24> im(width, height);
+
+    for (unsigned y = 0; y < height; ++y)
+      for (unsigned x = 0; x < width; ++x) {
+        if (fread(&im.buffer[y * width + x].r, 1, 1, input) != 1)
+          return {};
+        if (fread(&im.buffer[y * width + x].g, 1, 1, input) != 1)
+          return {};
+        if (fread(&im.buffer[y * width + x].b, 1, 1, input) != 1)
+          return {};
+      }
+
+    if (max != 255)
+      for (unsigned v = 0; v < width * height; ++v) {
+        im.buffer[v].r = ((uint16_t)im.buffer[v].r * 255) / max;
+        im.buffer[v].g = ((uint16_t)im.buffer[v].g * 255) / max;
+        im.buffer[v].b = ((uint16_t)im.buffer[v].b * 255) / max;
+      }
+
+    return im;
+
+  }
+
+}