如何将 BufferedImage 保存到 pgm 文件？

Question

I looked through the internet but I could not find an answer. I have a pgm file which I use as a BufferedImage to do a convolution (I use JAI for that) but I am having trouble in saving it back to a pgm file. So far I used following code to save:

JAI.create("filestore", newImage, outputFileName);

With that I get a pgm file but when I open the image IfranView tells me that it is a TIF file with incorrect extension. What do I need to change?

I appreciate any help! Please provide code examples if possible. Thanks everyone.

Kind regards, Staniel

Answer 1

BufferedImage bufferedImage = ImageIO.read(new File("input file directory...image.png"));

ImageIO.write(bufferedImage, "pgm", new File("output file directory.....image.pgm"));

This should take a buffered image (jpeg, png...etc) and convert it properly to a pgm.

EDIT: The JAI Plugin which allows for .pgm files to be used with ImageIO can be found at http://www.oracle.com/technetwork/java/index.html

Answer 2

Here's an example I found. Not tested.

// Create the OutputStream.
OutputStream out = new FileOutputStream(fileToWriteTo);
// Create the ParameterBlock.
PNMEncodeParam param = new PNMEncodeParam();
param.setRaw(true.equals("raw"));
//Create the PNM image encoder.
ImageEncoder encoder = ImageCodec.createImageEncoder("PNM", out, param);

See Writing PNM Files .

Answer 3

I found the answer. I already added the external JAI imageio to my library.

ImageIO.write(bufferedImage, "pnm", new File("output file directory.....image.pgm"));

Instead of "pgm" it should say "pnm". The new file will automatically have the pgm extension.

Answer 4

Maybe late, but I just wrote one. A simple PGM writer taking a 2d-double array with values in range [0.0,1.0].

    public static void WritePGM(string fileName, double[,] bitmap)
    {
        var width = bitmap.GetLength(0);
        var height = bitmap.GetLength(1);
        var header = "P5\n" + width + " " + height + "\n255\n";
        var writer = new BinaryWriter(new FileStream(fileName, FileMode.Create));
        writer.Write(System.Text.Encoding.ASCII.GetBytes(header));
        for (var j = 0; j < height; j++)
        {
            for (var i = width-1; i >= 0; i--)
            {
                var c = (byte)(System.Math.Max(System.Math.Min(1.0, bitmap[i, j]), 0.0) * 255.0);
                writer.Write(c);
            }
        }
        writer.Close();
    }

Answer 5

您可以在这里找到外部JAI ImageIO库： https : //bintray.com/jai-imageio/maven/jai-imageio-core-standalone/view