org.apache.shindig.gadgets.rewrite.image

Class BasicImageRewriter

java.lang.Object

org.apache.shindig.gadgets.rewrite.image.BasicImageRewriter

All Implemented Interfaces:

ResponseRewriter

public class BasicImageRewriter
extends Object
implements ResponseRewriter

Rewrite images to more efficiently compress their content. Can output to a different format file for better efficiency.

Security Note: Uses the Sanselan library to parse image content and metadata to avoid security issues in the ImageIO library. Uses ImageIO for output.

Field Summary

Fields

Modifier and Type	Field and Description
static String	CONTENT_TYPE

Constructor Summary

Constructors

Constructor and Description
BasicImageRewriter(OptimizerConfig config)

Method Summary

Methods

Modifier and Type	Method and Description
protected void	applyOptimizer(HttpResponseBuilder response, org.apache.sanselan.ImageFormat imageFormat, JpegImageUtils.JpegImageParams jpegImageParams, BufferedImage image, OptimizerConfig config)
protected void	enforceUnreadableImageRestrictions(Uri uri, HttpResponseBuilder response) An image could not be read from the content.
protected boolean	isImageUri(Uri uri) Ensures that the URI points to an image, before continuing.
protected boolean	isSupportedContent(HttpResponseBuilder response)
protected boolean	isSupportedImageResult(HttpResponseBuilder response, Uri uri)
protected BufferedImage	readBmp(HttpResponseBuilder response)
protected BufferedImage	readGif(HttpResponseBuilder response)
protected BufferedImage	readImage(org.apache.sanselan.ImageFormat imageFormat, HttpResponseBuilder response)
protected BufferedImage	readJpeg(HttpResponseBuilder response)
protected BufferedImage	readPng(HttpResponseBuilder response)
BufferedImage	resizeImage(BufferedImage image, Integer requestedWidth, Integer requestedHeight, int extraWidth, int extraHeight) Two-step image resize.
void	rewrite(HttpRequest request, HttpResponseBuilder response, Gadget gadget) Rewrites the response.
void	updateResponse(HttpResponseBuilder response, BufferedImage image) If the image is resized, the request needs to change so that the optimizer can make sensible image size-related decisions down the pipeline.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

CONTENT_TYPE

public static final String CONTENT_TYPE

See Also:

Constant Field Values

Constructor Detail

BasicImageRewriter

@Inject
public BasicImageRewriter(OptimizerConfig config)

Method Detail

rewrite

public void rewrite(HttpRequest request,
           HttpResponseBuilder response,
           Gadget gadget)

Description copied from interface: ResponseRewriter

Rewrites the response.

Specified by:

rewrite in interface ResponseRewriter

Parameters:

request - The request that was made.

response - The response generated as a result of the request.

gadget - The gadget that made the request. This parameter may be null.

updateResponse

public void updateResponse(HttpResponseBuilder response,
                  BufferedImage image)
                    throws IOException

If the image is resized, the request needs to change so that the optimizer can make sensible image size-related decisions down the pipeline. GIF images are rewritten as PNGs though, so as not to include the dependency on the GIF decoder.

Parameters:

response - the base response that will be modified with the resized image

image - the resized image that needs to be substituted for the original image from the response

Throws:

IOException

resizeImage

public BufferedImage resizeImage(BufferedImage image,
                        Integer requestedWidth,
                        Integer requestedHeight,
                        int extraWidth,
                        int extraHeight)

Two-step image resize.

The first step scales the image so that the smaller of the vertical and horizontal scaling ratios is satisfied. For square images the two ratios are equal and we leave it at that. For rectangular images, this leaves a part of the target image rectangle that is not covered, and we need to proceed to step 2.

The second step stretches the image along the dimension that came in short after the first step to fully cover the target image rectangle.

Parameters:

image - the image to resize

requestedWidth - the width in pixels of the requested resulting image

requestedHeight - the height in pixels of the requested resulting image

extraWidth - the width (in pixels) to add on top of the original image

extraHeight - the height (in pixels) to add on top of the original image

Returns:

the image obtained by stretching the original image so that its new dimensions are requestedWidth and requestedHeight

applyOptimizer

protected void applyOptimizer(HttpResponseBuilder response,
                  org.apache.sanselan.ImageFormat imageFormat,
                  JpegImageUtils.JpegImageParams jpegImageParams,
                  BufferedImage image,
                  OptimizerConfig config)
                       throws IOException

Throws:

IOException

isSupportedImageResult

protected boolean isSupportedImageResult(HttpResponseBuilder response,
                             Uri uri)

isSupportedContent

protected boolean isSupportedContent(HttpResponseBuilder response)

isImageUri

protected boolean isImageUri(Uri uri)

Ensures that the URI points to an image, before continuing.

Parameters:

uri - the URI to check

enforceUnreadableImageRestrictions

protected void enforceUnreadableImageRestrictions(Uri uri,
                                      HttpResponseBuilder response)

An image could not be read from the content. Normally this is fine unless the content-type states that this is an image in which case it could be an attack. If either the filetype or the MIME-type indicate that image content should be available but we failed to read it, then return an error response.

readImage

protected BufferedImage readImage(org.apache.sanselan.ImageFormat imageFormat,
                      HttpResponseBuilder response)
                           throws org.apache.sanselan.ImageReadException,
                                  IOException

Throws:

org.apache.sanselan.ImageReadException

IOException

readBmp

protected BufferedImage readBmp(HttpResponseBuilder response)
                         throws org.apache.sanselan.ImageReadException,
                                IOException

Throws:

org.apache.sanselan.ImageReadException

IOException

readPng

protected BufferedImage readPng(HttpResponseBuilder response)
                         throws org.apache.sanselan.ImageReadException,
                                IOException

Throws:

org.apache.sanselan.ImageReadException

IOException

readGif

protected BufferedImage readGif(HttpResponseBuilder response)
                         throws org.apache.sanselan.ImageReadException,
                                IOException

Throws:

org.apache.sanselan.ImageReadException

IOException

readJpeg

protected BufferedImage readJpeg(HttpResponseBuilder response)
                          throws org.apache.sanselan.ImageReadException,
                                 IOException

Throws:

org.apache.sanselan.ImageReadException

IOException