[ImageIO Tools] Writing float data as TIFF

[Andreas Jaeger]

When working with single-band float data (i.e. data that does not
represent pixels, but, say, precipitation), encoding an image and
decoding it again does not work correctly. Looks to me like a byte
order problem, at first glance. I'm using JAI ImageIO plugin for
TIFF. Anybody who sees my mistake, or knows a workaround?

Andreas

--
---------------------------------------------
Andreas Jaeger
http://afi.uni-muenster.de
afi - Institut für Agrar- und Forstinformatik
an der Universität Münster
---------------------------------------------

import com.sun.media.imageio.plugins.tiff.*;
import java.awt.*;
import java.awt.color.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.imageio.metadata.*;
import javax.imageio.stream.*;
import javax.swing.*;

/**
* Test illustrating problems when working with float samples and
* the ImageIO Tools TIFFWriter.
*/
public class FloatSampleTIFFTest {

public static void main(String[] args) throws IOException {
// Create the data simulation including noData values
float[] data = new float[220 * 60];
for (int i = 0; i < 220; i++) {
for (int j = 0; j < 60; j++) {
if (j + i > 250) {
data[i + j * 220] = -9999.0f;
} else {
data[i + j * 220] = (i + j);
}
}
}

// Wrap the data as a displayable image
SampleModel sm = new BandedSampleModel(DataBuffer.TYPE_FLOAT, 220, 60, 1);
DataBuffer db = new DataBufferFloat(data, data.length);
WritableRaster wr = Raster.createWritableRaster(sm, db, null);
BufferedImage bi = new BufferedImage(new FloatCM(-9999.0f, 0.0f, 250.0f), wr, false, null);

// Write out the image using ImageIO Tools TIFF encoder
ImageWriter iw = (ImageWriter) ImageIO.getImageWritersByMIMEType("image/tiff").next();
File tiffFile = new File(System.getProperty("java.io.tmpdir"), "floatSample.tif");
System.out.println("Writing output to " + tiffFile.getAbsolutePath());
ImageOutputStream ios = new MemoryCacheImageOutputStream(new FileOutputStream(tiffFile));
iw.setOutput(ios);
TIFFImageWriteParam iwp = (TIFFImageWriteParam) iw.getDefaultWriteParam();
// iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
// iwp.setCompressionType("Deflate");
IIOMetadata imd = iw.getDefaultImageMetadata(new ImageTypeSpecifier(bi), iwp);
iw.write(null, new IIOImage(bi, null, imd), iwp);
ios.flush();
ios.close();

// Re-read image to check data integrity, using ImageIO Tools TIFF decoder
ImageReader ir = (ImageReader) ImageIO.getImageReadersByMIMEType("image/tiff").next();
ImageInputStream iis = new MemoryCacheImageInputStream(new FileInputStream(tiffFile));
ir.setInput(iis);
int w = ir.getWidth(0);
int h = ir.getHeight(0);
ImageReadParam irp = ir.getDefaultReadParam();
SampleModel sm2 = new BandedSampleModel(DataBuffer.TYPE_FLOAT, w, h, 1);
DataBuffer db2 = new DataBufferFloat(new float[w * h], w * h);
WritableRaster wr2 = Raster.createWritableRaster(sm2, db2, null);
BufferedImage bi2 = new BufferedImage(new FloatCM(-9999.0f, 0.0f, 250.0f), wr2, false, null);
irp.setDestination(bi2);
bi2 = ir.read(0, irp);
iis.close();

// Display both images
JFrame jfr = new JFrame("Testing GeoTIFFs with Float Samples");
jfr.getContentPane().setLayout(new GridLayout(1, 0));
jfr.getContentPane().add(new JLabel(new ImageIcon(bi)));
jfr.getContentPane().add(new JLabel(new ImageIcon(bi2)));
jfr.pack();
jfr.show();
jfr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

/**
* Dirty hack to support float sample data in images.
*/
public static class FloatCM extends ColorModel {

private float noData;
private float min;
private float max;
private Color minColor;
private Color maxColor;
private Color noDataColor;

public FloatCM(float noData, float min, float max) {
this(noData, min, max, Color.YELLOW, Color.BLUE, Color.RED);
}

public FloatCM(float noData, float min, float max, Color minColor, Color maxColor, Color noDataColor) {
super(32, new int[] {8, 8, 8, 8}
, ColorSpace.getInstance(ColorSpace.CS_sRGB), true, false, Transparency.TRANSLUCENT, DataBuffer.TYPE_FLOAT);
this.noData = noData;
this.min = min;
this.max = max;
this.minColor = minColor;
this.maxColor = maxColor;
this.noDataColor = noDataColor;
}

public int getAlpha(int pixel) {
return (pixel & 0xff000000) >> 24;
}

public int getRed(int pixel) {
return (pixel & 0x00ff0000) >> 16;
}

public int getGreen(int pixel) {
return (pixel & 0x0000ff00) >> 8;
}

public int getBlue(int pixel) {
return (pixel & 0x000000ff);
}

public int getRGB(int pixel) {
return pixel;
}

public int getAlpha(Object inData) {
return getAlpha(getRGB(inData));
}

public int getRed(Object inData) {
return getRed(getRGB(inData));
}

public int getGreen(Object inData) {
return getGreen(getRGB(inData));
}

public int getBlue(Object inData) {
return getBlue(getRGB(inData));
}

public int getRGB(Object inData) {
float val = ((float[]) inData)[0];
if (val == noData) {
return noDataColor.getRGB();
} else if (val <= min) {
return minColor.getRGB();
} else if (val >= max) {
return maxColor.getRGB();
} else {
float fac = (val - min) / (max - min);
int alpha = Math.round(minColor.getAlpha() + fac * (maxColor.getAlpha() - minColor.getAlpha()));
int red = Math.round(minColor.getRed() + fac * (maxColor.getRed() - minColor.getRed()));
int green = Math.round(minColor.getGreen() + fac * (maxColor.getGreen() - minColor.getGreen()));
int blue = Math.round(minColor.getBlue() + fac * (maxColor.getBlue() - minColor.getBlue()));
return ((alpha & 0xff) << 24) | ((red & 0xff) << 16) | ((green & 0xff) << 8) | (blue & 0xff);
}
}

public ColorModel coerceData(WritableRaster raster, boolean isAlphaPremultiplied) {
if (! isAlphaPremultiplied) {
return this;
}
return super.coerceData(raster, isAlphaPremultiplied);
}

public boolean isCompatibleRaster(Raster raster) {
return isCompatibleSampleModel(raster.getSampleModel());
}

public boolean isCompatibleSampleModel(SampleModel sm) {
return sm.getDataType() == DataBuffer.TYPE_FLOAT;
}

}

}