Writing javafx.scene.image.Image to file?

Question

How would I go about writing a javafx.scene.image.Image image to a file. I know you can use ImageIO on BufferedImages but is there any way to do it with a javafx Image?

Answer 1

Just convert it to a BufferedImage first, using javafx.embed.swing.SwingFXUtils:

Image image = ... ; // javafx.scene.image.Image
String format = ... ;
File file = ... ;
ImageIO.write(SwingFXUtils.fromFXImage(image, null), format, file);

Answer 2

Almost 3 years later and I now have the knowledge to do and answer this. Yes the original answer was also valid but it involved first converting the image to a BufferedImage and I ideally wanted to avoid swing entirely. While this does output the raw RGBA version of the image that's good enough for what I needed to do. I actually could just use raw BGRA since I was writing the software to open the result but since gimp can't open that I figure I'd convert it to RGBA.

Image img = new Image("file:test.png");
int width = (int) img.getWidth();
int height = (int) img.getHeight();
PixelReader reader = img.getPixelReader();
byte[] buffer = new byte[width * height * 4];
WritablePixelFormat<ByteBuffer> format = PixelFormat.getByteBgraInstance();
reader.getPixels(0, 0, width, height, format, buffer, 0, width * 4);
try {
    BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("test.data"));
    for(int count = 0; count < buffer.length; count += 4) {
        out.write(buffer[count + 2]);
        out.write(buffer[count + 1]);
        out.write(buffer[count]);
        out.write(buffer[count + 3]);
    }
    out.flush();
    out.close();
} catch(IOException e) {
    e.printStackTrace();
}

Answer 3

JavaFX has no built-in method to do this.

To solve this problem, I implemented a very small (< 20KiB) library for writing PNG files: https://github.com/Glavo/SimplePNG

Usage:

Image img = new Image("path-to-image.jpg");

try (PNGWriter writer = new PNGWriter(Files.newOutputStream(Path.of("output.png")))) {
    writer.write(PNGJavaFXUtils.asArgbImage(img));
}

// Or you can use the shortcut:
// PNGJavaFXUtils.writeImage(img, Path.of("output.png"));

It has no dependencies and can work on the JRE that only have java.base.

I avoid the dependence on Java AWT (java.desktop) through it.