Add utility to write bitmap

Summary: Extract this function. Will add code that can write a texture to bitmap

Reviewed By: EricGriffith

Differential Revision: D63259599

fbshipit-source-id: 0ced538629791dbb1ed2271a7da8e021fead568c

IGLU/bitmap/BitmapWriter.cpp

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <IGLU/bitmap/BitmapWriter.h>
+
+#include <fstream>
+#include <igl/Common.h>
+
+namespace igl::iglu {
+namespace {
+struct BMPHeader {
+  // Bitmap file header
+  uint16_t signature = 0x4D42; // Signature ("BM" in ASCII), default value 0x4D42 for BMP format
+  uint32_t fileSize = 0;
+  uint16_t reserved1 = 0;
+  uint16_t reserved2 = 0;
+  uint32_t dataOffset = sizeof(BMPHeader); // Offset to the start of image data
+
+  // DIB header (Bitmap information header)
+  uint32_t headerSize = 40; // Size of the DIB header
+  int32_t imageWidth = 0;
+  int32_t imageHeight = 0;
+  uint16_t colorPlanes = 1; // Number of color planes
+  uint16_t bitsPerPixel = 24;
+  uint32_t compression = 0; // Compression method (initialized to 0 for no compression)
+  uint32_t imageSizeBytes = 0;
+  int32_t horizontalResolution = 0; // Horizontal resolution in pixels per meter
+  int32_t verticalResolution = 0; // Vertical resolution in pixels per meter
+  uint32_t numColors = 0; // Number of colors in the color palette
+  uint32_t importantColors = 0; // Number of important colors used
+} __attribute__((packed));
+
+} // namespace
+
+void writeBitmap(const char* filename, const uint8_t* imageData, uint32_t width, uint32_t height) {
+  std::ofstream file;
+  file.open(filename, std::ios::out | std::ios::binary);
+  if (!IGL_VERIFY(file)) {
+    return;
+  }
+
+  uint32_t imageSize = width * height * 3;
+
+  BMPHeader header{
+      .fileSize = static_cast<uint32_t>(sizeof(BMPHeader) + imageSize),
+      .imageWidth = static_cast<int32_t>(width),
+      .imageHeight = static_cast<int32_t>(height),
+      .imageSizeBytes = static_cast<uint32_t>(imageSize),
+  };
+
+  file.write(reinterpret_cast<const char*>(&header), sizeof(header));
+  file.write(reinterpret_cast<const char*>(imageData), imageSize);
+  file.close();
+}
+
+} // namespace igl::iglu

IGLU/bitmap/BitmapWriter.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <cstdint>
+
+namespace igl::iglu {
+
+void writeBitmap(const char* filename, const uint8_t* imageData, uint32_t width, uint32_t height);
+
+} // namespace igl::iglu