Java - Convert RAW to JPG/PNG

Question

I have an image captured by a camera, in RAW BGRA format (byte array). How can I save it to disk, as a JPG/PNG file?

I've tried with ImageIO.write from Java API, but I got error IllegalArgumentException (image = null)

CODE:

try
{
    InputStream input = new ByteArrayInputStream(img);
    BufferedImage bImageFromConvert = ImageIO.read(input);

    String path = "D:/image.jpg";

    ImageIO.write(bImageFromConvert, "jpg", new File(path));
}
catch(Exception ex)
{
    System.out.println(ex.toString());
}

Note that "img" is the RAW byte array, and that is NOT null.

Answer 1

The problem is that ImageIO.read does not support raw RGB (or BGRA in your case) pixels. It expects a file format , like BMP, PNG or JPEG, etc.

In your code above, this causes bImageFromConvert to become null , and this is the reason for the error you see.

If you have a byte array in BGRA format, try this:

// You need to know width/height of the image
int width = ...;
int height = ...;

int samplesPerPixel = 4;
int[] bandOffsets = {2, 1, 0, 3}; // BGRA order

byte[] bgraPixelData = new byte[width * height * samplesPerPixel];

DataBuffer buffer = new DataBufferByte(bgraPixelData, bgraPixelData.length);
WritableRaster raster = Raster.createInterleavedRaster(buffer, width, height, samplesPerPixel * width, samplesPerPixel, bandOffsets, null);

ColorModel colorModel = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB), true, false, Transparency.TRANSLUCENT, DataBuffer.TYPE_BYTE);

BufferedImage image = new BufferedImage(colorModel, raster, colorModel.isAlphaPremultiplied(), null);

System.out.println("image: " + image); // Should print: image: BufferedImage@<hash>: type = 0 ...

ImageIO.write(image, "PNG", new File(path));

Note that JPEG is not a good format for storing images with alpha channel. While it is possible, most software will not display it properly. So I suggest using PNG instead.

Alternatively, you could remove the alpha channel, and use JPEG.

Answer 2

With Matlab you can convert all types of images with 2 lines of code:

img=imread('example.CR2');
imwrite(img,'example.JPG');