From 925e7641e7fb75b41f5e6f9d4b0258a4e84beddb Mon Sep 17 00:00:00 2001
From: Jan Sladek <Jan.Sladek@mni.thm.de>
Date: Thu, 12 Mar 2015 15:19:26 +0100
Subject: [PATCH] Made the Extraction if image information in ImageUtils.java
faster. Closes #15353.
---
src/main/java/de/thm/arsnova/ImageUtils.java | 91 +++++++++++++++-----
1 file changed, 69 insertions(+), 22 deletions(-)
diff --git a/src/main/java/de/thm/arsnova/ImageUtils.java b/src/main/java/de/thm/arsnova/ImageUtils.java
index 9bef59585..5365e6d0c 100644
--- a/src/main/java/de/thm/arsnova/ImageUtils.java
+++ b/src/main/java/de/thm/arsnova/ImageUtils.java
@@ -25,8 +25,6 @@ import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
import javax.imageio.ImageIO;
@@ -41,18 +39,18 @@ import de.thm.arsnova.entities.Answer;
* Util class for image operations.
*
* @author Daniel Vogel (daniel.vogel@mni.thm.de)
- *
+ * @author Jan Sladek (jan.sladek@mni.thm.de)
*/
public class ImageUtils {
// Or whatever size you want to read in at a time.
private static final int CHUNK_SIZE = 4096;
- /**
- * {@link Pattern} used to check if a {@link String} starts with the
- * Base64-Mimetype Prefix and to extract information from the {@link String}.
- */
- public static final Pattern BASE64_IMAGE_PREFIX_PATTERN = Pattern.compile("data:image/(.*);base64,(.*)");
+ /** Base64-Mimetype-Prefix start */
+ public static final String IMAGE_PREFIX_START = "data:image/";
+
+ /** Base64-Mimetype-Prefix middle part */
+ public static final String IMAGE_PREFIX_MIDDLE = ";base64,";
/* default value is 200 pixel in width, set the value in the configuration file */
private static int THUMB_WIDTH = 200;
@@ -108,14 +106,52 @@ public class ImageUtils {
* @return true if the string is a potentially a base 64 encoded image.
*/
public static boolean isBase64EncodedImage(String maybeImage) {
+ return extractImageInfo(maybeImage) != null;
+ }
+
+ /**
+ * Extracts information(extension and the raw-image) from a {@link String}
+ * representing a base64-encoded image and returns it as a two-dimensional
+ * {@link String}-array, or null if the passed in {@link String} is not a
+ * valid base64-encoded image.
+ *
+ * @param maybeImage
+ * a {@link String} representing a base64-encoded image.
+ * @return two-dimensional {@link String}-array containing the information
+ * "extension" and the "raw-image-{@link String}"
+ */
+ public static String[] extractImageInfo(final String maybeImage) {
if (maybeImage == null) {
- return false;
+ return null;
}
else if (maybeImage.isEmpty()) {
- return false;
+ return null;
+ }
+ else {
+ if (!maybeImage.startsWith(IMAGE_PREFIX_START)) {
+ return null;
+ }
+ else {
+ final int extensionStartIndex = IMAGE_PREFIX_START.length();
+ final int extensionEndIndex = maybeImage.indexOf(IMAGE_PREFIX_MIDDLE);
+
+ final String imageWithoutPrefix = maybeImage.substring(extensionEndIndex);
+
+ if (!imageWithoutPrefix.startsWith(IMAGE_PREFIX_MIDDLE)) {
+ return null;
+ }
+ else {
+ final String[] imageInfo = new String[2];
+ final String extension = maybeImage.substring(extensionStartIndex, extensionEndIndex);
+ final String imageString = imageWithoutPrefix.substring(IMAGE_PREFIX_MIDDLE.length());
+
+ imageInfo[0] = extension;
+ imageInfo[1] = imageString;
+
+ return imageInfo;
+ }
+ }
}
- else
- return BASE64_IMAGE_PREFIX_PATTERN.matcher(maybeImage).matches();
}
/**
@@ -128,18 +164,19 @@ public class ImageUtils {
* the new width
* @param height
* the new height
- * @return The rescaled Image as Base64-encoded {@link String}
+ * @return The rescaled Image as Base64-encoded {@link String}, returns null
+ * if the passed-on image isn't in a valid format (a Base64-Image).
*/
public static String createCover(String originalImageString, final int width, final int height) {
- if (!isBase64EncodedImage(originalImageString)) return null;
+ if (!isBase64EncodedImage(originalImageString)) {
+ return null;
+ }
else {
- Matcher imageMatcher = BASE64_IMAGE_PREFIX_PATTERN.matcher(originalImageString);
- if (!imageMatcher.find()) {
- // shouldn't ever happen, because the regex is already checked.
- return null;
- }
- String extension = imageMatcher.group(1);
- String base64String = imageMatcher.group(2);
+ final String[] imgInfo = extractImageInfo(originalImageString);
+
+ // imgInfo isn't null and contains two fields, this is checked by "isBase64EncodedImage"-Method
+ final String extension = imgInfo[0];
+ final String base64String = imgInfo[1];
byte[] imageData = Base64.decodeBase64(base64String);
try {
@@ -183,11 +220,21 @@ public class ImageUtils {
}
}
- public static void generateThumbnailImage(Answer answer) {
+ /**
+ * Generates a thumbnail image in the {@link Answer}, if none is present.
+ *
+ * @param answer
+ * the {@link Answer} where the thumbnail should be added.
+ * @return true if the thumbnail image didn't exist before calling this
+ * method, false otherwise
+ */
+ public static boolean generateThumbnailImage(Answer answer) {
if (!isBase64EncodedImage(answer.getAnswerThumbnailImage())) {
final String thumbImage = createCover(answer.getAnswerImage(), THUMB_WIDTH, THUMB_HEIGHT);
answer.setAnswerThumbnailImage(thumbImage);
+ return true;
}
+ return false;
}
/**
--
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