java - 如何使用 Google App Engine Blobstore 压缩图像

Question

我们有一个应用程序可以为来自 blobstore 的一系列图像提供服务。一个示例在这里:

http://lh4.ggpht.com/f76xUkRZLRkb_Qz5uu82TX3LoBRh4eYb9hxYwMRMLCk5ghO_OL0DW2v4rRnkewUyDWfBuBttgbUvuJJXwtFQosEB=s0

这是一个巨大的 png，因此下载为 536K。

如果我们将它的大小调整为 400，它仍然很大 (263k):

http://lh4.ggpht.com/f76xUkRZLRkb_Qz5uu82TX3LoBRh4eYb9hxYwMRMLCk5ghO_OL0DW2v4rRnkewUyDWfBuBttgbUvuJJXwtFQosEB=s400

我们如何以某种更好的方式请求或存储图片压缩？我们的应用程序有一个移动客户端，正在等待273K 让它变得非常慢。

Answer 1

有Images API .压缩和调整图像大小:

// get image from blobstore
ImagesService imagesService = ImagesServiceFactory.getImagesService();
Image oldImage = ImagesServiceFactory.makeImageFromBlob(blobKey); 

// compress & resize it
OutputSettings settings = new OutputSettings(ImagesService.OutputEncoding.JPEG);
settings.setQuality(90);
Transform transform = ImagesServiceFactory.makeResize(newWidth, newHeight) 
Image newImage = imagesService.applyTransform(transform, oldImage, settings);
byte[] blobData = newImage.getImageData();

//save data to blobstore
FileService fileService = FileServiceFactory.getFileService();
AppEngineFile file = fileService.createNewBlobFile("image/jpeg", someFilename);
FileWriteChannel writeChannel = fileService.openWriteChannel(file, true);
writeChannel.write(ByteBuffer.wrap(blobData));
writeChannel.closeFinally();

// get the blobKey to newly written data
BlobKey blobKey = fileService.getBlobKey(file);