Add a new tool extract_a_sub_image.cpp to extract a sub-image

CGAL_ImageIO/examples/CGALimageIO/CMakeLists.txt

@@ -16,6 +16,7 @@ if(CGAL_ImageIO_FOUND)
 
   create_single_source_cgal_program( "convert_raw_image_to_inr.cpp" )
   create_single_source_cgal_program( "test_imageio.cpp" )
+  create_single_source_cgal_program( "extract_a_sub_image.cpp" )
 else()
   message(STATUS "NOTICE: This demo needs the CGAL ImageIO library, and will not be compiled.")
 endif()

CGAL_ImageIO/examples/CGALimageIO/extract_a_sub_image.cpp

@@ -0,0 +1,46 @@
+#include <CGAL/ImageIO.h>
+#include <iostream>
+
+int main(int argc, char **argv) {
+  if (argc != 9) {
+    std::cerr << "Usage: extract_a_sub_image <input> <output> <xmin> <xmax> "
+                 "<ymin> <ymax> <zmin> <zmax>\n";
+    return argc != 1;
+  }
+  _image *image = ::_readImage(argv[1]);
+  if (!image)
+    return 2;
+  const auto xmin = std::stoul(argv[3]);
+  const auto xmax = std::stoul(argv[4]);
+  const auto ymin = std::stoul(argv[5]);
+  const auto ymax = std::stoul(argv[6]);
+  const auto zmin = std::stoul(argv[7]);
+  const auto zmax = std::stoul(argv[8]);
+  assert(xmin >= 0);
+  assert(ymin >= 0);
+  assert(zmin >= 0);
+  assert(xmax < image->xdim);
+  assert(ymax < image->ydim);
+  assert(zmax < image->zdim);
+
+  const int new_xdim = xmax + 1 - xmin;
+  const int new_ydim = ymax + 1 - ymin;
+  const int new_zdim = zmax + 1 - zmin;
+
+  auto *new_image = ::_createImage(new_xdim, new_ydim, new_zdim, image->vx,
+                                   image->vx, image->vx, image->vz, image->wdim,
+                                   image->wordKind, image->sign);
+  const auto* const data = static_cast<char*>(image->data);
+  auto* new_data = static_cast<char*>(new_image->data);
+  for (auto k = zmin; k < zmax; ++k)
+    for (auto j = ymin; j <= ymax; ++j)
+      for (auto i = xmin; i <= xmax; ++i) {
+        auto pos = data + image->wdim * (i + image->xdim * (j + image->zdim * k));
+        std::copy(pos, pos + image->wdim, new_data);
+        new_data += image->wdim;
+      }
+  auto r = ::_writeImage(new_image, argv[2]);
+  if(r != ImageIO_NO_ERROR) return 3;
+  ::_freeImage(image);
+  ::_freeImage(new_image);
+}