RGBIndex
public class ErrorDiffusionDithering extends ImageToImageOperation implements RGBIndex
GrayIntegerImage
and
RGBIntegerImage
objects.
For RGB images, a quantizer must be specified via setQuantizer(net.sourceforge.jiu.color.quantization.RGBQuantizer)
.
That quantizer must have been initialized (it must have searched for / given a palette that it can map to).
This class offers six predefined types of error diffusion dithering.
In addition, user-defined types can be integrated by providing a
information on how the error is to be distributed; see the
description of setTemplateData(int[][])
.
MemoryRGB24Image image = ...; // some RGB image OctreeColorQuantizer quantizer = new OctreeColorQuantizer(); quantizer.setInputImage(image); quantizer.setPaletteSize(120); quantizer.init(); ErrorDiffusionDithering edd = new ErrorDiffusionDithering(); edd.setTemplateType(ErrorDiffusionDithering.TYPE_STUCKI); edd.setQuantizer(quantizer); edd.setInputImage(image); edd.process(); PixelImage quantizedImage = edd.getOutputImage();
Gray8Image
object
is reduced to black and white using Floyd-Steinberg dithering.
Gray8Image image = ...; // some grayscale image ErrorDiffusionDithering edd = new ErrorDiffusionDithering(); edd.setGrayscaleOutputBits(1); edd.setInputImage(image); edd.process(); PixelImage ditheredImage = edd.getOutputImage(); // if you need something more specific than PixelImage: BilevelImage output = null; // ditheredImage should be a BilevelImage... if (ditheredImage instanceof BilevelImage { // ... and it is! output = (BilevelImage)ditheredImage; }
Several sources recommend Robert Ulichney's book Digital Halftoning for this topic (published by The MIT Press, ISBN 0-262-21009-6). Unfortunately, I wasn't able to get a copy (or the CD-ROM version published by Dr. Dobb's Journal).
Modifier and Type | Field | Description |
---|---|---|
private static int[][] |
BURKES_DATA |
|
static int |
DEFAULT_TYPE |
The default error diffusion type, to be used if none is specified by the user:
(@link #TYPE_FLOYD_STEINBERG}.
|
private int[] |
errorDen |
|
private int[] |
errorNum |
|
private static int[][] |
FLOYD_STEINBERG_DATA |
|
private int |
grayBits |
|
private int |
imageWidth |
|
static int |
INDEX_ERROR_DENOMINATOR |
The index of the denominator of the relative part of the error of a neighbor pixel.
|
static int |
INDEX_ERROR_NUMERATOR |
The index of the numerator of the relative part of the error of a neighbor pixel.
|
static int |
INDEX_X_POS |
The index for the horizontal position of a neighbor pixel.
|
static int |
INDEX_Y_POS |
The index for the vertical position of a neighbor pixel.
|
private int[] |
indexLut |
|
private static int[][] |
JARVIS_JUDICE_NINKE_DATA |
|
private int |
leftColumns |
|
private int |
newWidth |
|
private int |
numRows |
|
private RGBQuantizer |
quantizer |
|
private int |
rightColumns |
|
private static int[][] |
SIERRA_DATA |
|
private static int[][] |
STEVENSON_ARCE_DATA |
|
private static int[][] |
STUCKI_DATA |
|
private int[][] |
templateData |
|
static int |
TYPE_BURKES |
Constant for Burkes error diffusion.
|
static int |
TYPE_FLOYD_STEINBERG |
Constant for Floyd-Steinberg error diffusion.
|
static int |
TYPE_JARVIS_JUDICE_NINKE |
Constant for Burkes error diffusion.
|
static int |
TYPE_SIERRA |
Constant for Burkes error diffusion.
|
static int |
TYPE_STEVENSON_ARCE |
Constant for Burkes error diffusion.
|
static int |
TYPE_STUCKI |
Constant for Stucki error diffusion.
|
private boolean |
useTruecolorOutput |
INDEX_BLUE, INDEX_GREEN, INDEX_RED
Constructor | Description |
---|---|
ErrorDiffusionDithering() |
Creates a new object of this class and set the dithering type to
DEFAULT_TYPE . |
Modifier and Type | Method | Description |
---|---|---|
private static int |
adjust(int value,
int max) |
Clamps the argument value to interval 0..max.
|
private void |
fillBuffer(int channelIndex,
int rowIndex,
int[] dest,
int destOffset) |
Copies data from input image to argument buffer.
|
private void |
init(int[][] data,
int imageWidth) |
|
void |
process() |
Quantizes the input image, distributing quantization errors to neighboring
pixels.
|
private void |
process(Gray8Image in,
BilevelImage out) |
|
private void |
process(Gray8Image in,
Gray8Image out) |
|
private void |
process(RGB24Image in,
Paletted8Image out) |
|
private void |
process(RGB24Image in,
RGB24Image out) |
|
void |
setGrayscaleOutputBits(int numBits) |
Sets the number of bits to be in the output image when a grayscale image
is quantized.
|
void |
setQuantizer(RGBQuantizer q) |
Sets the color quantizer to be used (if the input image is
a truecolor image).
|
void |
setTemplateData(int[][] data) |
Set information on how errors are to be distributed by this error diffusion
dithering operation.
|
void |
setTemplateType(int type) |
Sets a new template type.
|
void |
setTruecolorOutput(boolean truecolor) |
When dithering an RGB input image, this method specifies whether the
output will be an
RGBIntegerImage
(true ) or a Paletted8Image (false ). |
canInputAndOutputBeEqual, ensureImagesHaveSameResolution, ensureInputImageIsAvailable, ensureOutputImageResolution, getInputImage, getOutputImage, setCanInputAndOutputBeEqual, setInputImage, setOutputImage
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
addProgressListener, addProgressListeners, getAbort, removeProgressListener, setAbort, setProgress, setProgress
public static final int TYPE_FLOYD_STEINBERG
public static final int TYPE_STUCKI
public static final int TYPE_BURKES
public static final int TYPE_SIERRA
public static final int TYPE_JARVIS_JUDICE_NINKE
public static final int TYPE_STEVENSON_ARCE
public static final int DEFAULT_TYPE
public static final int INDEX_X_POS
setTemplateData(int[][])
.public static final int INDEX_Y_POS
setTemplateData(int[][])
.public static final int INDEX_ERROR_NUMERATOR
setTemplateData(int[][])
.public static final int INDEX_ERROR_DENOMINATOR
setTemplateData(int[][])
.private static final int[][] FLOYD_STEINBERG_DATA
private static final int[][] STUCKI_DATA
private static final int[][] BURKES_DATA
private static final int[][] SIERRA_DATA
private static final int[][] JARVIS_JUDICE_NINKE_DATA
private static final int[][] STEVENSON_ARCE_DATA
private int grayBits
private int imageWidth
private int leftColumns
private int rightColumns
private int newWidth
private int numRows
private int[][] templateData
private int[] errorNum
private int[] errorDen
private int[] indexLut
private RGBQuantizer quantizer
private boolean useTruecolorOutput
public ErrorDiffusionDithering()
DEFAULT_TYPE
.private static int adjust(int value, int max)
value
- the value to be adjustedmax
- the maximum allowed value (minimum is always 0)private void fillBuffer(int channelIndex, int rowIndex, int[] dest, int destOffset)
channelIndex
- index of the channel of the input image from which data is to be copiedrowIndex
- index of the row of the input image from which data is to be copieddest
- the array to which data is to be copieddestOffset
- index of the first element in the dest array to which data will be copiedprivate void init(int[][] data, int imageWidth)
public void process() throws MissingParameterException, WrongParameterException
Gray8Image
(then setGrayscaleOutputBits(int)
must have been called to set a number of output bits between 1 and 7) objects and
RGB24Image
(then a quantizer must be specified using
setQuantizer(RGBQuantizer)
) objects.process
in class Operation
MissingParameterException
- if any mandatory parameter was not given to the operationWrongParameterException
- if at least one of the input parameters was
not initialized appropriately (values out of the valid interval, etc.)private void process(Gray8Image in, BilevelImage out)
private void process(Gray8Image in, Gray8Image out)
private void process(RGB24Image in, Paletted8Image out)
private void process(RGB24Image in, RGB24Image out)
public void setGrayscaleOutputBits(int numBits)
Gray8Image
, only values between 1 and 7
are valid.numBits
- the number of bits in the output imagepublic void setQuantizer(RGBQuantizer q)
q
- an object of a class implementing the RGBQuantizer interfacepublic void setTemplateData(int[][] data)
Error diffusion dithering works by quantizing each pixel and distributing the resulting error to neighboring pixels. Quantizing maps a pixel to another pixel. Each pixel is made up of one or more samples (as an example, three samples rorig, gorig and borig for the original pixel of an RGB image and rquant, gquant and bquant for the quantized pixel).
The process of quantization attempts to find a quantized pixel that is as close to the original as possible. In the ideal case, the difference between original and quantized pixel is zero for each sample. Otherwise, this quantization error is non-zero, positive or negative. Example: original pixel (12, 43, 33), quantized pixel (10, 47, 40); the error is (12 - 10, 43 - 47, 40 - 33) = (2, -4, 7). The error (2, -4, 7) is to be distributed to neighboring pixels.
The data
argument of this constructor describes how to do that.
It is a two-dimensional array of int values.
Each of the one-dimensional int arrays of data
describe
one neighboring pixel and the relative amount of the error that it gets.
That is why data.length
specifies the number of neighboring
pixels involved in distributing the error.
Let's call the pixel that was just quantized the current pixel.
It is at image position (x, y).
Each of the one-dimensional arrays that are part of data
must have a length of 4.
The meaning of these four values is now described.
The values can be accessed by the INDEX_xyz constants of this class.
These four values describe the position of one neighboring pixel and
the relative amount of the error that will be added to or subtracted
from it.
INDEX_X_POS
(0):
the difference between the horizontal position of the current pixel, x,
and the neighboring pixel; can take a positive or negative value,
or zero; exception: the y position of the current pixel is zero;
in that case, this value must be larger than zero, because
neighboring pixels that get part of the error must be to the right of
or below the current pixelINDEX_Y_POS
(1):
the difference between the vertical position of the current pixel, y,
and the neighboring pixel; must be equal to or larger than 0INDEX_ERROR_NUMERATOR
(2):
the numerator of the relative part of the error that wil be added
to this neighboring pixel; must not be equal to 0INDEX_ERROR_DENOMINATOR
(3):
the denominator of the relative part of the error that wil be added
to this neighboring pixel; must not be equal to 0data
array:
int[][] FLOYD_STEINBERG = {{ 1, 0, 7, 16}, {-1, 1, 3, 16}, { 0, 1, 5, 16}, { 1, 1, 1, 16}};Each of the one-dimensional arrays is of length 4. Accidentally, there are also four one-dimensional arrays. The number of arrays is up to the designer. The first array {1, 0, 7, 16} is interpreted as follows--go to the pixel with a horizontal difference of 1 and a vertical difference of 0 (so, the pixel to the right of the current pixel) and add 7 / 16th of the quantization error to it. Then go to the pixel at position (-1, 1) (one to the left, one row below the current row) and add 3 / 16th of the error to it. The other two one-dimensional arrays are processed just like that.
As you can see, the four relative errors 1/16, 3/16, 5/16 and 7/16 sum up to 1 (or 16/16); this is in a precondition to make sure that the error is distributed completely.
data
- contains a description of how the error is to be distributedpublic void setTruecolorOutput(boolean truecolor)
RGBIntegerImage
(true
) or a Paletted8Image
(false
).truecolor
- true if truecolor output is wantedpublic void setTemplateType(int type)
type
- int value, one of the TYPE_xyz constants of this classIllegalArgumentException
- if the argument is not of the TYPE_xyz constants