Convert image byte[] to a file

Question

I am trying to convert an image(png,jpg,tiff,gif) to a File on disk.When I view it after storing it on file, I cannot see the file.

Here is some code I have tried based on other forum discussions:

byte[] inFileName = org.apache.commons.io.FileUtils.readFileToByteArray(new File("c:/test1.png"));

InputStream inputStream = new ByteArrayInputStream(inFilename);
..String fileName="test.png";
Writer writer = new FileWriter(fileName);
IOUtils.copy(inputStream, writer,"ISO-8859-1");

This creates a png file I cannot see.

I tried using ImageIO based on some other discussion but can't get it to work.Any help is appreciated.

    Image inImage = ImageIO.read(new ByteArrayInputStream(inFilename));
BufferedImage outImage = new BufferedImage(100, 100,
            BufferedImage.TYPE_INT_RGB); 
 OutputStream os = new FileOutputStream(fileName);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(os);
//encoder.encode(inImage);

Do mine eyes deceive me? Are you **really** writing a PNG file with a text encoding? — Matt Ball, Aug 26 '11 at 22:32
http://stackoverflow.com/questions/1580038/byte-array-to-image-file — Vijay, Aug 26 '11 at 22:37

score 5 · Answer 1 · answered Aug 26 '11 at 22:41

5

You should write it to FileOutputStream directly.

InputStream input = new ByteArrayInputStream(bytes);
OutputStream output = new FileOutputStream(fileName);
IOUtils.copy(input, output);

Images are binary data, not character data. You should not use a Writer, it's for character data, but you should use an OutputStream, it's for binary data. The BufferedImage and JPEGImageEncoder are pointless as long as you don't want to manipulate the image.

answered Aug 26 '11 at 22:41

BalusC

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+1 as I was unable to answer this question myself, was busy reattaching my jaw after reading the code... – Matt Ball Aug 26 '11 at 22:44
@BlausC I have a use case for Android OS to copy a .png image as an app asset. So rather than use IOUtils from Apache library, can you point me in the right direction to copy the image bytes to a file with Android methods, so I can use FileProvider() to share the image with another app user? I am trying to copy image to a File in the app's internal storage directory. – AJW May 13 '20 at 22:15
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@AJW: https://stackoverflow.com/search?q=%5Bjava%5D+write+inputstream+to+outputstream --> https://stackoverflow.com/q/43157/157882 – BalusC May 13 '20 at 22:26

score 0 · Answer 2 · answered Aug 26 '11 at 22:45

What are you trying to do; read a PNG image and save it as a JPEG?

Your first code snippet is not going to work, because you are using a Writer to write the data. A Writer is only suited for writing text files. PNG and JPEG files contain binary data, not text.

You can load an image using the ImageIO API:

BufferedImage img = ImageIO.read(new File("C:/test.png"));

And then write it in another format using the ImageIO API:

ImageIO.write(img, "jpg", new File("C:/test.jpg"));

Convert image byte[] to a file

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