Experimental implementation of Base64 encoded DataURL string. Probably not a good idea.. ;-)

sandbox/sandbox-imageio/src/main/java/com/twelvemonkeys/imageio/stream/Base64DataURLImageInputStreamSpi.java

@@ -0,0 +1,65 @@
+package com.twelvemonkeys.imageio.stream;
+
+import com.twelvemonkeys.io.StringInputStream;
+import com.twelvemonkeys.io.enc.Base64Decoder;
+import com.twelvemonkeys.io.enc.DecoderStream;
+
+import javax.imageio.spi.ImageInputStreamSpi;
+import javax.imageio.stream.FileCacheImageInputStream;
+import javax.imageio.stream.ImageInputStream;
+import javax.imageio.stream.MemoryCacheImageInputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.Charset;
+import java.util.Locale;
+
+/**
+ * Base64DataURLImageInputStreamSpi
+ *
+ * @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
+ * @author last modified by $Author: haraldk$
+ * @version $Id: Base64DataURLImageInputStreamSpi.java,v 1.0 03.09.13 09:35 haraldk Exp$
+ */
+public class Base64DataURLImageInputStreamSpi extends ImageInputStreamSpi {
+    // This is generally a bad idea, because:
+    //  - It is bound to String.class, and not all strings are base64 encoded data URLs.
+    //  - It's better to just create a decoder stream from the base64 stream, and use what's already in ImageIO....
+
+    public Base64DataURLImageInputStreamSpi() {
+        super("TwelveMonkeys", "0.1-BETA", String.class);
+    }
+
+    @Override
+    public ImageInputStream createInputStreamInstance(final Object input, final boolean useCache, final File cacheDir) throws IOException {
+        String string = (String) input;
+
+        InputStream stream = createStreamFromBase64(string);
+
+        return useCache && cacheDir != null ? new FileCacheImageInputStream(stream, cacheDir) : new MemoryCacheImageInputStream(stream);
+    }
+
+    private InputStream createStreamFromBase64(String string) {
+        if (!string.startsWith("data:")) {
+            throw new IllegalArgumentException(String.format("Not a data URL: %s", string));
+        }
+
+        int index = string.indexOf(';');
+        if (index < 0 || !string.regionMatches(index + 1, "base64,", 0, "base64,".length())) {
+            throw new IllegalArgumentException(String.format("Not base64 encoded: %s", string));
+        }
+
+        int offset = index + "base64,".length() + 1;
+        return new DecoderStream(new StringInputStream(string.substring(offset), Charset.forName("UTF-8")), new Base64Decoder());
+    }
+
+    @Override
+    public boolean canUseCacheFile() {
+        return true;
+    }
+
+    @Override
+    public String getDescription(Locale locale) {
+        return "Service provider that instantiates a FileCacheImageInputStream or MemoryCacheImageInputStream from a Base64 encoded data string";
+    }
+}