[doc] update README, make examples self-contained

Author: fangq

README.md

@@ -9,7 +9,7 @@
 * Compatibility: MATLAB R2008a or newer, or Octave 4.0 and newer
 * JNIfTI Specification Version: V1 Draft-2 (https://neurojson.org/jnifti/draft2)
 * Acknowledgement: This project is supported by US National Institute of Health (NIH)
-  grant [U24-NS124027 (NeuroJSON)](https://reporter.nih.gov/project-details/10308329)
+  grant [U24-NS124027 (NeuroJSON)](https://neurojson.org)
 
 ## Overview
 
@@ -20,7 +20,7 @@ files (`.hdr/.img` and `.hdr.gz/.img.gz`).
 
 More importantly, this is a toolbox that converts NIfTI data to its JSON-based
 replacement, JNIfTI (`.jnii` for text-based and `.bnii` for binary-based), defined
-by the JNIfTI specification (https://github.com/NeuroJSON/jnift). JNIfTI is a 
+by the JNIfTI specification (https://github.com/NeuroJSON/jnifti). JNIfTI is a
 much more flexible, human-readable and extensible file format compared to the
 more rigid and opaque NIfTI format, making the data much easier to manipulate
 and share.
@@ -50,9 +50,13 @@ ZMat toolbox (https://github.com/NeuroJSON/zmat), although it is optional.
 ### `nii2jnii` - To convert a NIfTI-1/2 file to a JNIfTI file or data structure
 Example:
 ```
+  img = uint16(reshape(1:10*30*20, [10, 30, 20]));  % create sample data
+  savenifti(img, 'test.nii');              % save sample data as an example nii file
+  savenifti(img, 'test.nii.gz');           % save sample data as an example nii.gz file
+
   nii=nii2jnii('test.nii', 'nii');         % read a .nii file as a nii structure
   nii=nii2jnii('test.nii.gz');             % read a .nii.gz file as a jnii structure
-  nii2jnii('test.nii.gz', 'newdata.jnii') ;% read a .nii.gz file and convert to a text-JNIfTI file  
+  nii2jnii('test.nii.gz', 'newdata.jnii') ;% read a .nii.gz file and convert to a text-JNIfTI file
   nii2jnii('test.nii.gz', 'newdata.bnii','compression','zlib'); % read a .nii.gz file and convert to a binary-JNIfTI file with compression
 ```
 ### `loadnifti` - To read a NIfTI-1/2 (.nii or .nii.gz) file (alias to `nii2jnii`)
@@ -66,7 +70,7 @@ Example:
 ```
   savenifti(img, 'test.nii.gz');        % save an array img to a compressed nifti file
   savenifti(img, 'test.nii', 'nifti2'); % save an array img to a nifti-2 file file
-  savenifti(img, 'test.nii', header);   % save an array img with an existing header
+  savenifti(img, 'test.nii', nii.hdr);  % save an array img with an existing header
 ```
 ### `loadjnifti` - To read a JNIfTI (.jnii or .bnii) file
 Example:
@@ -81,6 +85,8 @@ Example:
   jnii = jnifticreate(uint8(magic(10)), 'Name', '10x10 magic matrix');
   savejnifti(jnii, 'magic10.jnii');
   savejnifti(jnii, 'magic10_debug.bnii', 'Compression', 'gzip');
+  savejnifti(jnii, 'test.jnii', 'Compression', 'zlib');
+  savejnifti(jnii, 'test.bnii', 'Compression', 'zlib');
 ```
 ### `jnii2nii` - To convert a JNIfTI file or data structure to a NIfTI-1/2 file
 Example: