A few small modifications:

Closes Issue #18: CMakeLists.txt allows disabling SIMD instruction for compilations targeting ARM and other platforms.
Closes Issue #21: Added some text in README.md to clarify the need to use an escape character before { and }.
Closes Issue #22: Added some text in README.md to clarify how the downsampling option -downsamp should be used for the case of 422 (Obviously more work on documentation is needed).
Closes Issue #23: It looks like some older versions of ffprobe is sensitive to the header of ppm, so I modified the header slightly to make it acceptable.  I think the new format should be supported by more applications.

CMakeLists.txt

@@ -2,11 +2,21 @@ cmake_minimum_required(VERSION 3.10.0)
 
 project (openjph DESCRIPTION "Open source implementation of JPH" LANGUAGES CXX)
 
+option(OJPH_DISABLE_INTEL_SIMD "Disables the use of SIMD instructions and associated files" OFF)
+
 set(CMAKE_CXX_STANDARD 11)
 if (MSVC)
 	SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc /D \"_CRT_SECURE_NO_WARNINGS\"")
 endif()
 
+if (OJPH_DISABLE_INTEL_SIMD)
+	if (MSVC)
+		SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /D \"OJPH_DISABLE_INTEL_SIMD\"")
+	else()
+		SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DOJPH_DISABLE_INTEL_SIMD")
+	endif()
+endif()
+
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/../bin)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/../bin)
 
@@ -17,7 +27,12 @@ file(GLOB SSE_SOURCES "src/core/transform/*_sse.cpp")
 file(GLOB SSE2_SOURCES "src/core/transform/*_sse2.cpp")
 file(GLOB AVX_SOURCES "src/core/transform/*_avx.cpp")
 file(GLOB AVX2_SOURCES "src/core/transform/*_avx2.cpp")
-add_library(openjph SHARED ${SOURCES} ${SSE_SOURCES} ${SSE2_SOURCES} ${AVX_SOURCES} ${AVX2_SOURCES})
+
+if (OJPH_DISABLE_INTEL_SIMD)
+    add_library(openjph SHARED ${SOURCES})
+else()
+    add_library(openjph SHARED ${SOURCES} ${SSE_SOURCES} ${SSE2_SOURCES} ${AVX_SOURCES} ${AVX2_SOURCES})
+endif()
 
 if (MSVC)
 	set_source_files_properties(src/core/transform/ojph_colour_avx.cpp PROPERTIES COMPILE_FLAGS "/arch:AVX")

README.md

@@ -50,45 +50,63 @@ The generated library and executables will be in the bin folder.
 The library can now be compiled to javascript/wasm.  For this purpose, a small wrapper file (ojph_wrapper.cpp) has been written to interface between javascript and C++; the wrapper currently supports decoding only.  A small demo page demonstrating the script can be accessed [here](https://openjph.org/javascript/demo.html).
 
 Compilation needs the [emscripten](https://emscripten.org/) tools. One way of using these tools is to install them on your machine, and activate them using 
-```base
-source emsdk_env.sh
-```  
+
+	source emsdk_env.sh
+
 before compilation.  Alternatively, if you are a docker user, the you can launch a docker session using script provided at ```subprojects/js/emscripten-docker.sh```; this script will download a third-party docker image that has the emscripten tools integrated in it -- Thanks to [Chris](https://github.com/chafey) for the suggesting and providing these tools.  
 
 The javascript decoder can be compiled using
-```bash
-cd subprojects/js/build
-emmake cmake ..
-make
-```
+
+	cd subprojects/js/build
+	emmake cmake ..
+	make
+
 
 The compilation creates libopenjph.js and libopenjph.wasm in subprojects/js/html folder.  That html folder also has the demo webpage index.html and a compressed image test.j2c which the script in index.html decodes.  To run the demo webpage on your machine, you need a webserver running on the machine -- Due to security reasons, javascript engines running in a browser cannot access local files on the machine.  You can use the ```emrun``` command, provided with the emscripten
 tools, by issuing the command
-```base
-emrun index.html
-```
+
+	emrun index.html
+
 from inside the html folder; the default port is 6931.
 Alternatively, a simple python webserver can be run using
-```python
-python -m SimpleHTTPServer 8000
-```  
+
+	python -m SimpleHTTPServer 8000
+
 also from inside the html folder.  Here, 8000 is the port number at which the webserver will be listening.  The webpage can then be accessed by open 127.0.0.1:8000 in you browser.   Any browser supporting webassembly can be used to view this webpage; examples include Firefox, Chrome, Safari, and Edge, on a desktop, mobile, or tablet.
 
 # Visual Studio Code Remote Containers #
 
 Visual Studio Code Remote Containers are now available with OpenJPH.  These scripts/configuration files are provided by [Chris](https://github.com/chafey) -- Thank you Chris, and I must say I am not familiar with them.
 The scripts, in the ```.devcontainer``` folder, will build a docker image that can be used with visual studio code as a development environment.
 
+# Compiling for ARM and other platforms #
+
+To compile for platforms where x86_64 SIMD instructions are not supported, such as on ARM, we need to disable SIMD instructions; this can be achieved using
+
+    cd build
+    cmake -DCMAKE_BUILD_TYPE=Release -DOJPH_DISABLE_INTEL_SIMD=ON ../
+    make
+
+As I do not have an ARM board, I tested this using QEMU for aarch64 architecture, targeting a Cortex-A57 CPU. The code worked without issues, but because the ARM platform is emulated, the whole process was slow.
+
 # Usage Example #
 
-**Note**: in Kakadu, pairs of data in command line arguments represent columns,rows. Here, a pair represents x,y information.  On a different note, in reversible compression, quantization is not supported.
+Here are some usage examples:
 
     ojph_compress -i input_file.ppm -o output_file.j2c -num_decomps 5 -block_size {64,64} -precincts {128,128},{256,256} -prog_order CPRL -colour_trans true -qstep 0.05
     ojph_compress -i input_file.yuv -o output_file.j2c -num_decomps 5 -reversible true -dims {3840,2160} -num_comps 3 -signed false -bit_depth 10 -downsamp {1,1},{2,2}
 
     ojph_expand -i input_file.j2c -o output_file.ppm
     ojph_expand -i input_file.j2c -o output_file.yuv
 
+**Notes**: 
+
+* Issuing ojph\_compress or ojph\_expand without arguments prints a short usage statement.
+* In reversible compression, quantization is not supported.
+* On Linux and MacOS, but NOT Windows, { and } need to be escaped; i.e, we need to write \\\{ and \\\}.  So, -block\_size {64,64} must be written as -block\_size \\\{64,64\\\}.
+* When the source is a .yuv file, use -downsamp {1,1} for 4:4:4 sources. For 4:2:2 downsampling, specify -downsamp {1,1},{2,1}, and for 4:2:0 subsampling specify -downsamp {1,1},{2,2}. The source must have already been downsampled (i.e., OpenJPH does not downsample the source before compression, but can compress downsampled sources).
+* In Kakadu, pairs of data in command line arguments represent columns,rows. Here, a pair represents x,y information.
+
 # Related #
 
 The standard is available [here](https://www.itu.int/rec/T-REC-T.814/en).  It is currently free of charge; I do not know if this is temporary or permanent -- **Update 25/12/2019**: it is no longer available free of charge. 

src/apps/apps.xcodeproj/xcshareddata/xcschemes/ojph_compress.xcscheme

@@ -182,8 +182,8 @@
             isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
-            argument = "-num_decomps 4"
-            isEnabled = "YES">
+            argument = "-num_decomps 6"
+            isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-num_decomps 2"
@@ -215,7 +215,7 @@
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-prog_order CPRL"
-            isEnabled = "YES">
+            isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-block_size \{4,1024\}"
@@ -263,7 +263,7 @@
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-reversible true"
-            isEnabled = "YES">
+            isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-colour_trans false"
@@ -275,18 +275,22 @@
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-profile IMF"
-            isEnabled = "YES">
+            isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-profile BROADCAST"
             isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-tile_size \{1024,1024\}"
-            isEnabled = "YES">
+            isEnabled = "NO">
          </CommandLineArgument>
          <CommandLineArgument
             argument = "-i ARRI_AlexaDrums_3840x2160p_24_8b_P3_444_00000.ppm -o test.j2c -block_size \{32,32\} -precincts \{128,128\},\{256,256\}"
+            isEnabled = "NO">
+         </CommandLineArgument>
+         <CommandLineArgument
+            argument = "-i ARRI_AlexaDrums_3840x2160p_24_10b_bt709_444_00162.ppm -o test.j2c -profile IMF -block_size \{32,32\} -precincts \{128,128\},\{256,256\} -prog_order CPRL -reversible true"
             isEnabled = "YES">
          </CommandLineArgument>
       </CommandLineArguments>

src/apps/others/ojph_img_io.cpp

@@ -239,7 +239,7 @@ namespace ojph {
         OJPH_ERROR(0x030000021,
           "unable to open file %s for writing", filename);
 
-      fprintf(fh, "P5 %d %d %d\n", width, height, (1 << bit_depth) - 1);
+      fprintf(fh, "P5\n%d %d\n%d\n", width, height, (1 << bit_depth) - 1);
       buffer_size = width * bytes_per_sample;
       buffer = (ui8*)malloc(buffer_size);
     }
@@ -264,7 +264,7 @@ namespace ojph {
         OJPH_ERROR(0x030000022,
           "unable to open file %s for writing", filename);
       int result = //the number of written characters
-        fprintf(fh, "P6 %d %d %d\n", width, height, (1 << bit_depth) - 1);
+        fprintf(fh, "P6\n%d %d\n%d\n", width, height, (1 << bit_depth) - 1);
       if (result == 0)
         OJPH_ERROR(0x030000023, "error writing to file %s", filename);
       buffer_size = width * num_components * bytes_per_sample;

src/core/common/ojph_defs.h

@@ -58,7 +58,7 @@ typedef int64_t si64;
 /////////////////////////////////////////////////////////////////////////////
 #define OJPH_CORE_VER_MAJOR    0
 #define OJPH_CORE_VER_MINOR    6
-#define OJPH_CORE_VER_SUBMINOR 0
+#define OJPH_CORE_VER_SUBMINOR 1
 
 /////////////////////////////////////////////////////////////////////////////
 #define OJPH_INT_STRINGIFY(I) #I