将 Blob 转换为 JPG 并更新 Blob [英] Convert Blob to JPG and update blob

问题描述

我正在尝试读取 blob，将其转换为 JPG，然后写回 blob(它是通过引用传入的，但是在尝试在 TOAD 中编译时，我在 ImageIO.write 上遇到错误.

I'm trying to read in a blob, convert it to JPG and then write back to the blob (it is being passed in by reference, but when trying to compile in TOAD I get an error on ImageIO.write.

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED BANNADMIN.IMAGE_CONVERTER
   AS package uk.co.ImageUtil;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import oracle.sql.*;
import java.io.OutputStream;

public class ImageConverter {
    public static void convertImage(BLOB[] blob) {
       BufferedImage image = null;
       OutputStream outputStream = null;
        try {
            image = ImageIO.read(blob[0].getBinaryStream());

            outputStream = blob[0].setBinaryStream(0);

            ImageIO.write(image, "JPG", outputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        catch(IllegalArgumentException e) {
            e.printStackTrace();
        }
        finally {
            try {
                if (outputStream !== null) {
                    outputStream.flush();
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
/

如何将 BufferedImage 转换为 RenderedImage 以便将 JPG 版本写回 Blob?

How would I convert a BufferedImage into a RenderedImage so I can write the JPG version back into the Blob?

更新:错误信息是

[Error]  (1: 0): IMAGE_CONVERTER:28: cannot find symbol
[Error]  (1: 0): symbol  : method    write(java.awt.image.BufferedImage,java.lang.String,java.lang.Object)
[Error]  (1: 0): location: class javax.imageio.ImageIO
[Error]  (1: 0):             ImageIO.write(image, "jpg", outputStream);
[Error]  (1: 0):                    ^
[Error]  (1: 0): 1 error

推荐答案

结果证明这是一个简单的错误，ImageIO.write 接收了一个 RenderedImage，这意味着我必须将 BufferedImage 转换为 RenderedImage，并且我在 finally 块中编写了 !== 而不是 != .查看下面编译成功的内容

Turned out it was a simple mistake, ImageIO.write takes in a RenderedImage which meant I had to cast the BufferedImage to RenderedImage, and I had written !== instead of != in the finally block. See below for what compiles successfully

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED BANNADMIN.IMAGE_CONVERTER AS package uk.co.ImageUtil;

import javax.imageio.ImageIO;
import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import oracle.sql.*;
import java.io.OutputStream;
import java.sql.SQLException;

public class ImageConverter {
    /**
      * Take in a BLOB file (specified as an array parameter but we only ever use [0])
      * Read in the binary stream of the BLOB
      * Change the binary stream to jpg
      * Write the binary stream jpg to the BLOB
      * The BLOB parameter is passed in via out - so there is no need to return the BLOB, only edit it
      */
    public static void convertImage(BLOB[] blob) {
       BufferedImage bufferedImage = null;
       OutputStream outputStream = null;
        try {
            bufferedImage = ImageIO.read(blob[0].getBinaryStream());

            outputStream = blob[0].setBinaryStream(0);

            RenderedImage renderedImage = (RenderedImage)bufferedImage;

            ImageIO.write(renderedImage, "JPG", outputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
        catch (SQLException e) {
            e.printStackTrace();
        }
        catch(IllegalArgumentException e) {
            e.printStackTrace();
        }
        finally {
            try {
                if (outputStream != null) {
                    outputStream.flush();
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
/

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