The solution; This plugin that converts a Base64 PNG String and generates an image to the sdCard. Let’s go!
1. The Base64 Decoder
Get this blazing fast Base64 encode/decoder class called MiGBase64. Download it from SourceForge. Create a folder called ‘util’ within your project’s src/ folder. Place the downloaded class there.
2. The java
Create a folder called ‘org/apache/cordova’ within your project’s src/ folder.
Create in it a Java file called “Base64ToPNG.java” with the following source code.
package org.apache.cordova;
/**
* A phonegap plugin that converts a Base64 String to a PNG file.
*
* @author mcaesar
* @lincese MIT.
*/
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.cordova.api.Plugin;
import org.apache.cordova.api.PluginResult;
import org.json.JSONArray;
import android.os.Environment;
import java.io.*;
import org.json.JSONException;
import org.json.JSONObject;
import util.Base64;
public class Base64ToPNG extends Plugin {
@Override
public PluginResult execute(String action, JSONArray args, String callbackId) {
if (!action.equals("saveImage")) {
return new PluginResult(PluginResult.Status.INVALID_ACTION);
}
try {
String b64String = "";
if (b64String.startsWith("data:image")) {
b64String = args.getString(0).substring(21);
} else {
b64String = args.getString(0);
}
JSONObject params = args.getJSONObject(1);
//Optional parameter
String filename = params.has("filename")
? params.getString("filename")
: "b64Image_" + System.currentTimeMillis() + ".png";
String folder = params.has("folder")
? params.getString("folder")
: Environment.getExternalStorageDirectory() + "/Pictures";
Boolean overwrite = params.has("overwrite")
? params.getBoolean("overwrite")
: false;
return this.saveImage(b64String, filename, folder, overwrite, callbackId);
} catch (JSONException e) {
e.printStackTrace();
return new PluginResult(PluginResult.Status.JSON_EXCEPTION, e.getMessage());
} catch (InterruptedException e) {
e.printStackTrace();
return new PluginResult(PluginResult.Status.ERROR, e.getMessage());
}
}
private PluginResult saveImage(String b64String, String fileName, String dirName, Boolean overwrite, String callbackId) throws InterruptedException, JSONException {
try {
//Directory and File
File dir = new File(dirName);
if (!dir.exists()) {
dir.mkdirs();
}
File file = new File(dirName, fileName);
//Avoid overwriting a file
if (!overwrite && file.exists()) {
return new PluginResult(PluginResult.Status.OK, "File already exists!");
}
//Decode Base64 back to Binary format
byte[] decodedBytes = Base64.decode(b64String.getBytes());
//Save Binary file to phone
file.createNewFile();
FileOutputStream fOut = new FileOutputStream(file);
fOut.write(decodedBytes);
fOut.close();
return new PluginResult(PluginResult.Status.OK, "Saved successfully!");
} catch (FileNotFoundException e) {
return new PluginResult(PluginResult.Status.ERROR, "File not Found!");
} catch (IOException e) {
return new PluginResult(PluginResult.Status.ERROR, e.getMessage());
}
}
}
3. The Javascript
Write this JavaScript as Base64ToPNG.js to your project’s www folder. DONT forget to include a reference to it in your html files.
/**Works on all versions prior and including Cordova 1.6.1
* by mcaesar
* MIT license
*
*/
(function() {
/* This increases plugin compatibility */
var cordovaRef = window.PhoneGap || window.Cordova || window.cordova; // old to new fallbacks
/**
* The Java to JavaScript Gateway 'magic' class
*/
function Base64ToPNG() { }
/**
* Save the base64 String as a PNG file to the user's Photo Library
*/
Base64ToPNG.prototype.saveImage = function(b64String, params, win, fail) {
cordovaRef.exec(win, fail, "Base64ToPNG", "saveImage", [b64String, params]);
};
cordovaRef.addConstructor(function() {
if (!window.plugins) {
window.plugins = {};
}
if (!window.plugins.base64ToPNG) {
window.plugins.base64ToPNG = new Base64ToPNG();
}
});
})();
4. The plugins.xml file
Add the following to res/xml/plugins.xml file
<plugin name="Base64ToPNG" value="org.apache.cordova.Base64ToPNG"/>
5. Finally, HTML examples and the parameters
<button onclick="test();">No optional params required, Cowboy.</button> </br>
<button onclick="test2();">Make PNG with some parameters</button>
<script src="https://stackoverflow.com/questions/11388018/Base64ToPNG.js" type="text/javascript"></script>
<script type="text/javascript">
//May have a mime-type definition or not
var myBase64 = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="//a red dot
function test(){
//Illustrates how to use plugin with no optional parameters. Just the base64 Image.
window.plugins.base64ToPNG.saveImage(myBase64, {},
function(result) {
alert(result);
}, function(error) {
alert(error);
});
}
//No mimetype definition example
var myOtherBase64 = "iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
function test2(){
//Shows how to use optional parameters
window.plugins.base64ToPNG.saveImage(myBase64, {filename:"dot.png", overwrite: true},
function(result) {
alert(result);
}, function(error) {
alert(error);
});
}
</script>
Parameters
- filename: Name of the file to be generated. By default the same as the one in url.
- folder: Name of the directory to generate the file to. By default “sdcard/Pictures”
-
overwrite: If the file already exists, replace it. By default false.
I hope this answers some bothering questions. Happy coding!