diff --git a/CMakeLists.txt b/CMakeLists.txt
index 96546898..ee1c3758 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,6 +22,9 @@ endif()
 set(DIP_SHARED_LIBRARY ON CACHE BOOL "Build a shared library (off for static library)")
 set(BUILD_SHARED_LIBS ${DIP_SHARED_LIBRARY})
 
+# build bundled dependencies or use find_package?
+set(DIP_BUILD_BUNDLED_DEPENDENCIES ON CACHE BOOL "Build the bundled dependencies or use find_package otherwise")
+
 # Installation path
 set(CMAKE_INSTALL_PREFIX "${CMAKE_BUILD_TYPE}" CACHE PATH "Installation directory")
 set(DOCUMENTATION_OUTPUT share/doc/DIPlib)
diff --git a/dependencies/libics/CMakeLists.txt b/dependencies/libics/CMakeLists.txt
index 572f64bb..a24ebbd6 100644
--- a/dependencies/libics/CMakeLists.txt
+++ b/dependencies/libics/CMakeLists.txt
@@ -100,8 +100,8 @@ endif(UNIX)
 #endif()
 
 # DIPlib-specific zlib
-if(TARGET zlibstatic)
-   target_link_libraries(libics PRIVATE zlibstatic)
+if(TARGET ZLIB::ZLIB)
+   target_link_libraries(libics PRIVATE ZLIB::ZLIB)
    target_compile_definitions(libics PUBLIC -DICS_ZLIB)
 endif()
 
diff --git a/dependencies/libtiff/CMakeLists.txt b/dependencies/libtiff/CMakeLists.txt
index 8d08268e..2dd46696 100644
--- a/dependencies/libtiff/CMakeLists.txt
+++ b/dependencies/libtiff/CMakeLists.txt
@@ -378,7 +378,7 @@ set(MDI_SUPPORT TRUE)
 
 # ZLIB
 set(ZLIB_SUPPORT FALSE)
-if(TARGET zlibstatic)
+if(TARGET ZLIB::ZLIB)
   set(ZLIB_SUPPORT TRUE)
 endif()
 set(ZIP_SUPPORT ${ZLIB_SUPPORT})
@@ -468,10 +468,10 @@ if(M_LIBRARY)
   list(APPEND TIFF_LIBRARY_DEPS ${M_LIBRARY})
 endif()
 if(ZLIB_SUPPORT)
-  list(APPEND TIFF_LIBRARY_DEPS zlibstatic)
+  list(APPEND TIFF_LIBRARY_DEPS ZLIB::ZLIB)
 endif()
 if(JPEG_SUPPORT)
-  list(APPEND TIFF_LIBRARY_DEPS jpeg)
+  list(APPEND TIFF_LIBRARY_DEPS JPEG::JPEG)
 endif()
 if(JPEG12_LIBRARIES)
   list(APPEND TIFF_LIBRARY_DEPS ${JPEG12_LIBRARIES})
diff --git a/pydip/CMakeLists.txt b/pydip/CMakeLists.txt
index 145e7d3a..239a9528 100644
--- a/pydip/CMakeLists.txt
+++ b/pydip/CMakeLists.txt
@@ -1,5 +1,9 @@
 set(PYBIND11_PYTHON_VERSION ${PYTHON_VERSION}) # Avoid a warning message
-add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/pybind11" "${PROJECT_BINARY_DIR}/pybind11" EXCLUDE_FROM_ALL)
+if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+   add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/pybind11" "${PROJECT_BINARY_DIR}/pybind11" EXCLUDE_FROM_ALL)
+else()
+   find_package(pybind11 REQUIRED)
+endif()
 
 # Find sources
 file(GLOB DIP_PYTHON_SRC "${CMAKE_CURRENT_LIST_DIR}/src/*.cpp" "${CMAKE_CURRENT_LIST_DIR}/src/*.h")
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9b9df17b..43e189a2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -68,7 +68,15 @@ endif()
 # that uses DIPlib, hence we define a variable here that removes all of DocTest from the DIPlib sources.
 set(DIP_ENABLE_DOCTEST ON CACHE BOOL "Turn off to not include doctest.h in the library headers")
 if(DIP_ENABLE_DOCTEST)
-   target_include_directories(DIP PRIVATE "${PROJECT_SOURCE_DIR}/dependencies/doctest")
+   if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+      list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/dependencies/doctest")
+      add_library(doctest INTERFACE)
+      target_include_directories(doctest INTERFACE "${PROJECT_SOURCE_DIR}/dependencies")
+      add_library(doctest::doctest ALIAS doctest)
+   else()
+      find_package(doctest REQUIRED)
+   endif()
+   target_link_libraries(DIP PRIVATE doctest::doctest)
    target_compile_definitions(DIP PRIVATE
                               DIP_CONFIG_ENABLE_DOCTEST
                               DOCTEST_CONFIG_NO_SHORT_MACRO_NAMES
@@ -95,7 +103,12 @@ endif()
 set(HAS_128_INT ${HAS_128_INT} PARENT_SCOPE)
 
 # Eigen
-target_include_directories(DIP PRIVATE "${PROJECT_SOURCE_DIR}/dependencies/eigen3")
+if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+   target_include_directories(DIP PRIVATE "${PROJECT_SOURCE_DIR}/dependencies/eigen3")
+else()
+   find_package(Eigen3 REQUIRED)
+   target_include_directories(DIP PRIVATE ${EIGEN3_INCLUDE_DIR})
+endif()
 target_compile_definitions(DIP PRIVATE
                            EIGEN_MPL2_ONLY # This makes sure we only use parts of the Eigen library that use the MPL2 license or more permissive ones.
                            EIGEN_DONT_PARALLELIZE) # This to prevent Eigen algorithms trying to run in parallel -- we parallelize at a larger scale.
@@ -103,31 +116,51 @@ target_compile_definitions(DIP PRIVATE
 # zlib (for use in libics and libtiff)
 set(DIP_ENABLE_ZLIB ON CACHE BOOL "Enable zlib compression in ICS and TIFF (deflate)")
 if(DIP_ENABLE_ZLIB)
-   add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/zlib" "${PROJECT_BINARY_DIR}/zlib" EXCLUDE_FROM_ALL)
+   if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+      add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/zlib" "${PROJECT_BINARY_DIR}/zlib" EXCLUDE_FROM_ALL)
+      add_library(ZLIB::ZLIB ALIAS zlibstatic)
+   else()
+      find_package(ZLIB REQUIRED)
+   endif()
 endif()
 
 # libjpeg (for use in libtiff)
 set(DIP_ENABLE_JPEG ON CACHE BOOL "Enable JPEG file support and compression in TIFF")
 if(DIP_ENABLE_JPEG)
-   add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libjpeg" "${PROJECT_BINARY_DIR}/libjpeg" EXCLUDE_FROM_ALL)
-   target_link_libraries(DIP PRIVATE jpeg)
+   if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+      add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libjpeg" "${PROJECT_BINARY_DIR}/libjpeg" EXCLUDE_FROM_ALL)
+      add_library(JPEG::JPEG ALIAS jpeg)
+   else()
+      find_package(JPEG REQUIRED)
+   endif()
+   target_link_libraries(DIP PRIVATE JPEG::JPEG)
    target_compile_definitions(DIP PRIVATE DIP_CONFIG_HAS_JPEG)
 endif()
 
 # libics
 set(DIP_ENABLE_ICS ON CACHE BOOL "Enable ICS file support")
 if(DIP_ENABLE_ICS)
-   set(LIBICS_INCLUDE_CPP Off) # TODO: we should start using the C++ interface
-   add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libics" "${PROJECT_BINARY_DIR}/libics" EXCLUDE_FROM_ALL)
-   target_link_libraries(DIP PRIVATE libics)
+   if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+      set(LIBICS_INCLUDE_CPP Off) # TODO: we should start using the C++ interface
+      add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libics" "${PROJECT_BINARY_DIR}/libics" EXCLUDE_FROM_ALL)
+      add_library(ICS::ICS ALIAS libics)
+   else()
+      find_package(ICS REQUIRED)
+   endif()
+   target_link_libraries(DIP PRIVATE ICS::ICS)
    target_compile_definitions(DIP PRIVATE DIP_CONFIG_HAS_ICS)
 endif()
 
 # libtiff
 set(DIP_ENABLE_TIFF ON CACHE BOOL "Enable TIFF file support")
 if(DIP_ENABLE_TIFF)
-   add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libtiff" "${PROJECT_BINARY_DIR}/libtiff" EXCLUDE_FROM_ALL)
-   target_link_libraries(DIP PRIVATE tiff)
+   if(DIP_BUILD_BUNDLED_DEPENDENCIES)
+      add_subdirectory("${PROJECT_SOURCE_DIR}/dependencies/libtiff" "${PROJECT_BINARY_DIR}/libtiff" EXCLUDE_FROM_ALL)
+      add_library(TIFF::TIFF ALIAS tiff)
+   else()
+      find_package(TIFF REQUIRED)
+   endif()
+   target_link_libraries(DIP PRIVATE TIFF::TIFF)
    target_compile_definitions(DIP PRIVATE DIP_CONFIG_HAS_TIFF)
 endif()
 
@@ -157,8 +190,7 @@ install(DIRECTORY "${PROJECT_SOURCE_DIR}/include/" DESTINATION include
 # DIPlib unit tests
 if(DIP_ENABLE_DOCTEST)
    add_executable(unit_tests EXCLUDE_FROM_ALL "${CMAKE_CURRENT_LIST_DIR}/library/unit_tests.cpp")
-   target_include_directories(unit_tests PRIVATE "${PROJECT_SOURCE_DIR}/dependencies/doctest")
-   target_link_libraries(unit_tests PRIVATE DIP)
+   target_link_libraries(unit_tests PRIVATE DIP doctest::doctest)
    target_compile_definitions(unit_tests PRIVATE
                               DIP_IMPLEMENT_UNIT_TESTS
                               DIP_CONFIG_ENABLE_DOCTEST
@@ -171,7 +203,7 @@ if(DIP_ENABLE_DOCTEST)
          set_target_properties(unit_tests PROPERTIES INSTALL_RPATH "$ORIGIN")
       endif()
    else()
-      include("${PROJECT_SOURCE_DIR}/dependencies/doctest/doctest_force_link_static_lib_in_target.cmake")
+      include(doctest_force_link_static_lib_in_target.cmake)
       doctest_force_link_static_lib_in_target(unit_tests DIP) # This pulls in all object files from the static DIP library
    endif()
    add_custom_target(check COMMAND unit_tests)
diff --git a/src/analysis/findshift.cpp b/src/analysis/findshift.cpp
index e2daf95d..322c24e8 100644
--- a/src/analysis/findshift.cpp
+++ b/src/analysis/findshift.cpp
@@ -426,7 +426,7 @@ FloatArray FindShift(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/generation.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing the FindShift function") {
diff --git a/src/binary/binary_basic.cpp b/src/binary/binary_basic.cpp
index a84696a2..185fdd53 100644
--- a/src/binary/binary_basic.cpp
+++ b/src/binary/binary_basic.cpp
@@ -225,7 +225,7 @@ void BinaryAreaOpening(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing the binary morphological filters") {
diff --git a/src/binary/sup_inf_generator.cpp b/src/binary/sup_inf_generator.cpp
index 7e340e79..13a3f0a7 100644
--- a/src/binary/sup_inf_generator.cpp
+++ b/src/binary/sup_inf_generator.cpp
@@ -620,7 +620,7 @@ IntervalArray ConvexHullInterval2D() {
 }
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/testing.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing private function RotateBy45Degrees") {
diff --git a/src/color/color.cpp b/src/color/color.cpp
index b6b33a70..5e65aa47 100644
--- a/src/color/color.cpp
+++ b/src/color/color.cpp
@@ -395,7 +395,7 @@ void ColorSpaceManager::SetWhitePoint( dip::XYZ whitePoint ) {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/math.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing the ColorSpaceManager class") {
diff --git a/src/detection/hough.cpp b/src/detection/hough.cpp
index 5cd89558..4eaf48cb 100644
--- a/src/detection/hough.cpp
+++ b/src/detection/hough.cpp
@@ -325,7 +325,7 @@ FloatCoordinateArray FindHoughCircles(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/linear.h"
 #include "diplib/segmentation.h"
 #include "diplib/math.h"
diff --git a/src/distance/separable_dt.cpp b/src/distance/separable_dt.cpp
index f584b47f..30d3b29f 100644
--- a/src/distance/separable_dt.cpp
+++ b/src/distance/separable_dt.cpp
@@ -216,7 +216,7 @@ void SeparableDistanceTransform(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/math.h"
 #include "diplib/statistics.h"
 #include "diplib/generation.h"
diff --git a/src/file_io/ics.cpp b/src/file_io/ics.cpp
index 419c22b7..7a95f76a 100644
--- a/src/file_io/ics.cpp
+++ b/src/file_io/ics.cpp
@@ -816,7 +816,7 @@ void ImageWriteICS(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/testing.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing ICS file reading and writing" ) {
diff --git a/src/file_io/tiff_write.cpp b/src/file_io/tiff_write.cpp
index ab1989d6..d9913a0e 100644
--- a/src/file_io/tiff_write.cpp
+++ b/src/file_io/tiff_write.cpp
@@ -374,7 +374,7 @@ void ImageWriteTIFF(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/testing.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing TIFF file reading and writing" ) {
diff --git a/src/geometry/interpolation.cpp b/src/geometry/interpolation.cpp
index ea1b724c..42aae8d6 100644
--- a/src/geometry/interpolation.cpp
+++ b/src/geometry/interpolation.cpp
@@ -654,7 +654,7 @@ void Rotation(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/generation.h"
 #include "diplib/transform.h"
 #include "diplib/testing.h"
diff --git a/src/histogram/distribution.cpp b/src/histogram/distribution.cpp
index 961eb270..b0093d6f 100644
--- a/src/histogram/distribution.cpp
+++ b/src/histogram/distribution.cpp
@@ -244,7 +244,7 @@ void Distribution::SetSampling(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/random.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Distribution" ) {
diff --git a/src/histogram/histogram.cpp b/src/histogram/histogram.cpp
index efcbb7a4..2fd45b2f 100644
--- a/src/histogram/histogram.cpp
+++ b/src/histogram/histogram.cpp
@@ -593,7 +593,7 @@ Histogram& Histogram::Smooth( FloatArray sigma ) {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/random.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Histogram" ) {
diff --git a/src/library/copy_buffer.cpp b/src/library/copy_buffer.cpp
index 26d6a3e1..56c6728f 100644
--- a/src/library/copy_buffer.cpp
+++ b/src/library/copy_buffer.cpp
@@ -758,7 +758,7 @@ void ExpandBuffer(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include <numeric>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the CopyBuffer function") {
diff --git a/src/library/graph.cpp b/src/library/graph.cpp
index 7e0a4563..0a7e17ab 100644
--- a/src/library/graph.cpp
+++ b/src/library/graph.cpp
@@ -520,7 +520,7 @@ LowestCommonAncestorSolver::LowestCommonAncestorSolver( Graph const& graph )
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing dip::Graph") {
    dip::Image img( { 4, 5 }, 1, dip::DT_UINT8 );
diff --git a/src/library/image_copy.cpp b/src/library/image_copy.cpp
index 4b350188..9b5d3cd2 100644
--- a/src/library/image_copy.cpp
+++ b/src/library/image_copy.cpp
@@ -642,7 +642,7 @@ void Image::Fill( Image::Sample const& sample ) {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Image::SwapBytesInSample" ) {
    dip::Image img( { 5, 8 }, 3, dip::DT_SINT16 );
diff --git a/src/library/image_data.cpp b/src/library/image_data.cpp
index d1a39fc1..a13c70f3 100644
--- a/src/library/image_data.cpp
+++ b/src/library/image_data.cpp
@@ -746,7 +746,7 @@ CoordinatesComputer Image::IndexToCoordinatesComputer() const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/random.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Image::Forge" ) {
diff --git a/src/library/image_indexing.cpp b/src/library/image_indexing.cpp
index 5c0607af..309bb7dd 100644
--- a/src/library/image_indexing.cpp
+++ b/src/library/image_indexing.cpp
@@ -160,7 +160,7 @@ void DefineROI(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing image indexing") {
    // Note that this also tests parts of dip::Image::View and dip::Image::Pixel functionality, which is
diff --git a/src/library/image_manip.cpp b/src/library/image_manip.cpp
index 2c0864ae..bd1a053c 100644
--- a/src/library/image_manip.cpp
+++ b/src/library/image_manip.cpp
@@ -626,7 +626,7 @@ RangeArray Image::CropWindow( UnsignedArray const& sizes, String const& cropLoca
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing dip::Image dimension manipulation functions") {
    dip::Image src( { 5, 10, 15 }, 3 );
diff --git a/src/library/image_views.cpp b/src/library/image_views.cpp
index 0448b973..82abd421 100644
--- a/src/library/image_views.cpp
+++ b/src/library/image_views.cpp
@@ -430,7 +430,7 @@ Image::View::Iterator Image::View::end() const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/testing.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Image::Pixel and related classes" ) {
diff --git a/src/library/iterators.cpp b/src/library/iterators.cpp
index a02db9e1..6e06b1a5 100644
--- a/src/library/iterators.cpp
+++ b/src/library/iterators.cpp
@@ -19,7 +19,7 @@
  */
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/generic_iterators.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing ImageIterator and GenericImageIterator") {
diff --git a/src/library/neighborhood.cpp b/src/library/neighborhood.cpp
index 9b6ac954..35b600b1 100644
--- a/src/library/neighborhood.cpp
+++ b/src/library/neighborhood.cpp
@@ -485,7 +485,7 @@ NeighborList NeighborList::SelectForward( dip::uint procDim ) const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the NeighborList class") {
    dip::dfloat x = 1.2;
diff --git a/src/library/physical_dimensions.cpp b/src/library/physical_dimensions.cpp
index 64c3fb4f..69ff54e5 100644
--- a/src/library/physical_dimensions.cpp
+++ b/src/library/physical_dimensions.cpp
@@ -518,7 +518,7 @@ dip::String Units::StringRepresentation( bool unicode ) const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the dip::Units class") {
    // Note: further tested at the same time as dip::PhysicalQuantity below
diff --git a/src/library/pixel_table.cpp b/src/library/pixel_table.cpp
index 9ceaef9d..0a05dd4b 100644
--- a/src/library/pixel_table.cpp
+++ b/src/library/pixel_table.cpp
@@ -461,7 +461,7 @@ void PixelTable::AddDistanceToOriginAsWeights() {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the PixelTable class") {
    dip::PixelTable pt( "elliptic", dip::FloatArray{ 10.1, 12.7, 5.3 }, 1 );
diff --git a/src/library/types.cpp b/src/library/types.cpp
index baa21763..b8ccf41c 100644
--- a/src/library/types.cpp
+++ b/src/library/types.cpp
@@ -19,7 +19,7 @@
  */
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/library/types.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing the dip::bin class") {
diff --git a/src/library/unit_tests.cpp b/src/library/unit_tests.cpp
index 9e383026..0fb3a814 100644
--- a/src/library/unit_tests.cpp
+++ b/src/library/unit_tests.cpp
@@ -26,7 +26,7 @@
 #ifdef DIP_CONFIG_DOCTEST_IN_SHARED_LIB
 
 #define DOCTEST_CONFIG_IMPLEMENTATION_IN_DLL
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 #include "diplib.h"
 #include "diplib/linear.h"
@@ -51,7 +51,7 @@ int main( int argc, const char* const* argv ) {
 #else // !DIP_CONFIG_DOCTEST_IN_SHARED_LIB
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 #endif // DIP_CONFIG_DOCTEST_IN_SHARED_LIB
 
@@ -61,7 +61,7 @@ int main( int argc, const char* const* argv ) {
 
 #define DOCTEST_CONFIG_IMPLEMENTATION_IN_DLL
 #define DOCTEST_CONFIG_IMPLEMENT
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 #endif // DIP_CONFIG_DOCTEST_IN_SHARED_LIB
 
diff --git a/src/linear/convolution.cpp b/src/linear/convolution.cpp
index 4a909bb8..e60f4862 100644
--- a/src/linear/convolution.cpp
+++ b/src/linear/convolution.cpp
@@ -556,7 +556,7 @@ void GeneralConvolution(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 #include "diplib/generation.h"
 #include "diplib/iterators.h"
diff --git a/src/linear/finitediff.cpp b/src/linear/finitediff.cpp
index 3b899655..86a4c634 100644
--- a/src/linear/finitediff.cpp
+++ b/src/linear/finitediff.cpp
@@ -71,7 +71,7 @@ void FiniteDifference(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 #include "diplib/iterators.h"
 
diff --git a/src/linear/gauss.cpp b/src/linear/gauss.cpp
index 727d375a..b3053166 100644
--- a/src/linear/gauss.cpp
+++ b/src/linear/gauss.cpp
@@ -402,7 +402,7 @@ void GaussFT(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 #include "diplib/iterators.h"
 #include "diplib/testing.h"
diff --git a/src/linear/gaussiir.cpp b/src/linear/gaussiir.cpp
index 8ae26031..4ddd8131 100644
--- a/src/linear/gaussiir.cpp
+++ b/src/linear/gaussiir.cpp
@@ -795,7 +795,7 @@ void GaussIIR(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 #include "diplib/iterators.h"
 #include "diplib/testing.h"
diff --git a/src/linear/separate_filter.cpp b/src/linear/separate_filter.cpp
index c69cdcef..55226deb 100644
--- a/src/linear/separate_filter.cpp
+++ b/src/linear/separate_filter.cpp
@@ -128,7 +128,7 @@ OneDimensionalFilterArray SeparateFilter( Image const& c_in ) {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 //#include "diplib/timer.h"
 
diff --git a/src/mapping/lookup_table.cpp b/src/mapping/lookup_table.cpp
index 44f8241a..41b94fdb 100644
--- a/src/mapping/lookup_table.cpp
+++ b/src/mapping/lookup_table.cpp
@@ -459,7 +459,7 @@ Image::Pixel LookupTable::Apply( dfloat value, InterpolationMode interpolation )
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/iterators.h"
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::LookupTable" ) {
diff --git a/src/math/arithmetic.cpp b/src/math/arithmetic.cpp
index df06841e..d64ce6be 100644
--- a/src/math/arithmetic.cpp
+++ b/src/math/arithmetic.cpp
@@ -493,7 +493,7 @@ void Invert(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/math.h"
 #include "diplib/testing.h"
 
diff --git a/src/math/projection.cpp b/src/math/projection.cpp
index d1ec9f49..20958ecd 100644
--- a/src/math/projection.cpp
+++ b/src/math/projection.cpp
@@ -1361,7 +1361,7 @@ void PositionPercentile(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the projection function mechanics") {
    // Testing that the ProjectionScan framework works appropriately.
diff --git a/src/measurement/chain_code.cpp b/src/measurement/chain_code.cpp
index d88bc0b8..0f28fdc6 100644
--- a/src/measurement/chain_code.cpp
+++ b/src/measurement/chain_code.cpp
@@ -200,7 +200,7 @@ dip::Polygon ChainCode::Polygon() const {
 }
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 #include "diplib/pixel_table.h"
 #include "diplib/morphology.h"
diff --git a/src/measurement/image_chain_code.cpp b/src/measurement/image_chain_code.cpp
index 270fa082..0449e74f 100644
--- a/src/measurement/image_chain_code.cpp
+++ b/src/measurement/image_chain_code.cpp
@@ -220,7 +220,7 @@ void ChainCode::Image( dip::Image& out ) const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing chain code conversion to image and back") {
    dip::ChainCode cc;
diff --git a/src/measurement/measure_polygon.cpp b/src/measurement/measure_polygon.cpp
index 9d00ca50..cc2069de 100644
--- a/src/measurement/measure_polygon.cpp
+++ b/src/measurement/measure_polygon.cpp
@@ -324,7 +324,7 @@ dfloat Polygon::BendingEnergy() const {
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing chain code polygons") {
    dip::ChainCode cc;
diff --git a/src/measurement/measurement.cpp b/src/measurement/measurement.cpp
index 4a169be6..debaf553 100644
--- a/src/measurement/measurement.cpp
+++ b/src/measurement/measurement.cpp
@@ -401,7 +401,7 @@ StatisticsAccumulator SampleStatistics( Measurement::IteratorFeature const& feat
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE( "[DIPlib] testing dip::Measurement" ) {
 
diff --git a/src/measurement/polygon.cpp b/src/measurement/polygon.cpp
index 538363ff..a13f73fe 100644
--- a/src/measurement/polygon.cpp
+++ b/src/measurement/polygon.cpp
@@ -251,7 +251,7 @@ ConvexHull::ConvexHull( dip::Polygon const& polygon ) {
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing polygon manipulation") {
    dip::Polygon p;
diff --git a/src/morphology/basic.cpp b/src/morphology/basic.cpp
index 096d18b6..910431d7 100644
--- a/src/morphology/basic.cpp
+++ b/src/morphology/basic.cpp
@@ -874,7 +874,7 @@ void BasicMorphology(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/statistics.h"
 #include "diplib/iterators.h"
 
diff --git a/src/regions/label.cpp b/src/regions/label.cpp
index 6e9ce201..d20f7b16 100644
--- a/src/regions/label.cpp
+++ b/src/regions/label.cpp
@@ -425,7 +425,7 @@ dip::uint Label(
 } // namespace dip
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/generation.h"
 #include "diplib/statistics.h"
 #include "diplib/binary.h"
diff --git a/src/support/accumulators.cpp b/src/support/accumulators.cpp
index a97622e5..af6bf7dd 100644
--- a/src/support/accumulators.cpp
+++ b/src/support/accumulators.cpp
@@ -19,7 +19,7 @@
  */
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 #include "diplib/accumulators.h"
 #include "diplib/random.h"
diff --git a/src/support/gaussian_mixture.cpp b/src/support/gaussian_mixture.cpp
index 9e2952db..2752fb45 100644
--- a/src/support/gaussian_mixture.cpp
+++ b/src/support/gaussian_mixture.cpp
@@ -149,7 +149,7 @@ std::vector< GaussianParameters > GaussianMixtureModel(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/generation.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing GaussianMixtureModel") {
diff --git a/src/support/matrix.cpp b/src/support/matrix.cpp
index 1cb6544d..a2c1cc00 100644
--- a/src/support/matrix.cpp
+++ b/src/support/matrix.cpp
@@ -406,7 +406,7 @@ void Solve(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 
 DOCTEST_TEST_CASE("[DIPlib] testing the EigenDecomposition functions") {
    // Test generic symmetric code with 2x2 matrix
diff --git a/src/support/numeric.cpp b/src/support/numeric.cpp
index d16e1705..e1f43ff5 100644
--- a/src/support/numeric.cpp
+++ b/src/support/numeric.cpp
@@ -235,7 +235,7 @@ dfloat BesselYN(
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/library/clamp_cast.h"
 #include "diplib/saturated_arithmetic.h"
 
diff --git a/src/transform/fourier.cpp b/src/transform/fourier.cpp
index 7e235f50..4bb7d8ee 100644
--- a/src/transform/fourier.cpp
+++ b/src/transform/fourier.cpp
@@ -899,7 +899,7 @@ dip::uint OptimalFourierTransformSize( dip::uint size, dip::String const& which
 
 
 #ifdef DIP_CONFIG_ENABLE_DOCTEST
-#include "doctest.h"
+#include <doctest/doctest.h>
 #include "diplib/random.h"
 
 DOCTEST_TEST_CASE("[DIPlib] testing the OptimalFourierTransformSize function") {
diff --git a/tools/FindEigen3.cmake b/tools/FindEigen3.cmake
new file mode 100644
index 00000000..98ab43d9
--- /dev/null
+++ b/tools/FindEigen3.cmake
@@ -0,0 +1,83 @@
+# - Try to find Eigen3 lib
+#
+# This module supports requiring a minimum version, e.g. you can do
+#   find_package(Eigen3 3.1.2)
+# to require version 3.1.2 or newer of Eigen3.
+#
+# Once done this will define
+#
+#  EIGEN3_FOUND - system has eigen lib with correct version
+#  EIGEN3_INCLUDE_DIR - the eigen include directory
+#  EIGEN3_VERSION - eigen version
+
+# Copyright (c) 2006, 2007 Montel Laurent, <montel@kde.org>
+# Copyright (c) 2008, 2009 Gael Guennebaud, <g.gael@free.fr>
+# Copyright (c) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
+# Redistribution and use is allowed according to the terms of the 2-clause BSD license.
+
+if(NOT Eigen3_FIND_VERSION)
+  if(NOT Eigen3_FIND_VERSION_MAJOR)
+    set(Eigen3_FIND_VERSION_MAJOR 2)
+  endif(NOT Eigen3_FIND_VERSION_MAJOR)
+  if(NOT Eigen3_FIND_VERSION_MINOR)
+    set(Eigen3_FIND_VERSION_MINOR 91)
+  endif(NOT Eigen3_FIND_VERSION_MINOR)
+  if(NOT Eigen3_FIND_VERSION_PATCH)
+    set(Eigen3_FIND_VERSION_PATCH 0)
+  endif(NOT Eigen3_FIND_VERSION_PATCH)
+
+  set(Eigen3_FIND_VERSION
+      "${Eigen3_FIND_VERSION_MAJOR}.${Eigen3_FIND_VERSION_MINOR}.${Eigen3_FIND_VERSION_PATCH}")
+endif(NOT Eigen3_FIND_VERSION)
+
+macro(_eigen3_check_version)
+  file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h" _eigen3_version_header)
+
+  string(REGEX MATCH "define[ \t]+EIGEN_WORLD_VERSION[ \t]+([0-9]+)" _eigen3_world_version_match
+               "${_eigen3_version_header}")
+  set(EIGEN3_WORLD_VERSION "${CMAKE_MATCH_1}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MAJOR_VERSION[ \t]+([0-9]+)" _eigen3_major_version_match
+               "${_eigen3_version_header}")
+  set(EIGEN3_MAJOR_VERSION "${CMAKE_MATCH_1}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MINOR_VERSION[ \t]+([0-9]+)" _eigen3_minor_version_match
+               "${_eigen3_version_header}")
+  set(EIGEN3_MINOR_VERSION "${CMAKE_MATCH_1}")
+
+  set(EIGEN3_VERSION ${EIGEN3_WORLD_VERSION}.${EIGEN3_MAJOR_VERSION}.${EIGEN3_MINOR_VERSION})
+  if(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+    set(EIGEN3_VERSION_OK FALSE)
+  else(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+    set(EIGEN3_VERSION_OK TRUE)
+  endif(${EIGEN3_VERSION} VERSION_LESS ${Eigen3_FIND_VERSION})
+
+  if(NOT EIGEN3_VERSION_OK)
+
+    message(STATUS "Eigen3 version ${EIGEN3_VERSION} found in ${EIGEN3_INCLUDE_DIR}, "
+                   "but at least version ${Eigen3_FIND_VERSION} is required")
+  endif(NOT EIGEN3_VERSION_OK)
+endmacro(_eigen3_check_version)
+
+if(EIGEN3_INCLUDE_DIR)
+
+  # in cache already
+  _eigen3_check_version()
+  set(EIGEN3_FOUND ${EIGEN3_VERSION_OK})
+
+else(EIGEN3_INCLUDE_DIR)
+
+  find_path(
+    EIGEN3_INCLUDE_DIR
+    NAMES signature_of_eigen3_matrix_library
+    PATHS ${CMAKE_INSTALL_PREFIX}/include ${KDE4_INCLUDE_DIR}
+    PATH_SUFFIXES eigen3 eigen)
+
+  if(EIGEN3_INCLUDE_DIR)
+    _eigen3_check_version()
+  endif(EIGEN3_INCLUDE_DIR)
+
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(Eigen3 DEFAULT_MSG EIGEN3_INCLUDE_DIR EIGEN3_VERSION_OK)
+
+  mark_as_advanced(EIGEN3_INCLUDE_DIR)
+
+endif(EIGEN3_INCLUDE_DIR)
diff --git a/tools/FindICS.cmake b/tools/FindICS.cmake
new file mode 100644
index 00000000..be7ba45a
--- /dev/null
+++ b/tools/FindICS.cmake
@@ -0,0 +1,48 @@
+# Copyright (C) 2021 LuaDist.
+# Created by Peter Kapec <kapecp@gmail.com>
+# Modified by Cris Luengo to look for GLFW instead of FreeGLUT, and set a target.
+# Modified by Milian Wolff to look for ICS instead of GLFW, and set a target.
+# Redistribution and use of this file is allowed according to the terms of the MIT license.
+# For details see the COPYRIGHT file distributed with LuaDist.
+#  Note:
+#     Searching headers and libraries is very simple and is NOT as powerful as scripts
+#     distributed with CMake, because LuaDist defines directories to search for.
+#     Everyone is encouraged to contact the author with improvements. Maybe this file
+#     becomes part of CMake distribution sometime.
+
+# - Find ICS
+# Find the native ICS headers and libraries.
+#
+#  ICS_INCLUDE_DIRS - where to find libics.h
+#  ICS_LIBRARIES    - List of libraries when using ICS.
+#  ICS_FOUND        - True if ICS found.
+#  ICS::ICS        - Target to link to (automatically sets include directories and linked libraries)
+
+# Look for the header file.
+find_path(ICS_INCLUDE_DIR NAMES libics.h)
+
+# Look for the library.
+find_library(ICS_LIBRARY NAMES ics)
+
+# Handle the QUIETLY and REQUIRED arguments and set ICS_FOUND to TRUE if all listed variables are TRUE.
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(ICS DEFAULT_MSG ICS_LIBRARY ICS_INCLUDE_DIR)
+
+# Copy the results to the output variables.
+if(ICS_FOUND)
+   set(ICS_LIBRARIES ${ICS_LIBRARY})
+   set(ICS_INCLUDE_DIRS ${ICS_INCLUDE_DIR})
+   if (NOT TARGET ICS::ICS)
+      add_library(ICS::ICS UNKNOWN IMPORTED)
+      set_target_properties(ICS::ICS PROPERTIES
+                            INTERFACE_INCLUDE_DIRECTORIES "${ICS_INCLUDE_DIRS}"
+                            IMPORTED_LOCATION "${ICS_LIBRARY}")
+   endif()
+   message(STATUS "ICS found: ${ICS_LIBRARY} -- ${ICS_INCLUDE_DIR}")
+else()
+   set(ICS_LIBRARIES)
+   set(ICS_INCLUDE_DIRS)
+   message(STATUS "ICS not found")
+endif()
+
+mark_as_advanced(ICS_INCLUDE_DIRS ICS_LIBRARIES)