Question

我有以下代码上传图片并在网页上显示

// Show uploaded file in this placeholder
final Embedded image = new Embedded("Uploaded Image");
image.setVisible(false);

// Implement both receiver that saves upload in a file and
// listener for successful upload
class ImageUploader implements Receiver, SucceededListener {
    public File file;

    public OutputStream receiveUpload(String filename, String mimeType) {
        // Create upload stream
        FileOutputStream fos = null; // Stream to write to
        try {
            // Open the file for writing.
            file = new File(tmp_dir + "/" + filename);
            fos = new FileOutputStream(file);
        } catch (final java.io.FileNotFoundException e) {                  
            return null;
        }
        return fos; // Return the output stream to write to
    }

    public void uploadSucceeded(SucceededEvent event) {     
        // Show the uploaded file in the image viewer
        image.setVisible(true);             
        image.setSource(new FileResource(file));                
    }
};
ImageUploader receiver = new ImageUploader(); 

// Create the upload with a caption and set receiver later
Upload upload = new Upload("Upload Image Here", receiver);
upload.setButtonCaption("Start Upload");
upload.addSucceededListener(receiver);  

final FormLayout fl = new FormLayout();
fl.setSizeUndefined();
fl.addComponents(upload, image);

问题是，它显示了完整的分辨率，我想缩放（因此它保持成比例），它下降到180px宽度。图片也需要保存为原始的filename_resized.jpg，但我似乎无法按比例缩放。网上有几个指南谈论调整大小（但随后图片变形）或者它给Vaadin带来了一些问题。

更新：添加了scarl jar（来自this answer)）因为它很容易使用以下代码：

BufferedImage scaledImage = Scalr.resize(image, 200);

但是会出现以下错误：

The method resize(BufferedImage, int, BufferedImageOp...) in the type Scalr is not applicable for the arguments (Embedded, int)

我无法施放，因为Cannot cast from Embedded to BufferedImage错误

更新：使用以下代码我可以转换为正确的类型

File imageFile = (((FileResource) (image.getSource())).getSourceFile());
BufferedImage originalImage = ImageIO.read(imageFile) ;

BufferedImage scaledImage = Scalr.resize(originalImage, 200);

但现在我无法显示图片..

final FormLayout fl = new FormLayout();
fl.setSizeUndefined();       
fl.addComponents(upload, scaledImage);

因为错误The method addComponents(Component...) in the type AbstractComponentContainer is not applicable for the arguments (Upload, BufferedImage)

Answer 1

您无法直接使用第三方工具（如Scalr）直接使用Vaadin对象，而无需将其调整到另一个。＆＃34;嵌入式＆＃34;是一个Vaadin类，而SclaR期望一个＆＃34; BufferedImage＆＃34;。

因此，您首先需要从Embedded对象中提取File对象：

File imageFile = ((FileResource)(image.getSource()).getSourceFile();

然后，使用ImageIO将其加载到BufferedImage中，如您指向的链接（What is the best way to scale images in Java?）中所述

BufferedImage img = ImageIO.read(...); // load image

然后，你有了你正在寻找的BufferedImage对象。

使用Vaadin和Java缩放图像

1 个答案: