com.objectplanet.image
Class PngEncoder

java.lang.Object
  com.objectplanet.image.PngEncoder

public class PngEncoder
extends java.lang.Object

This PngEncoder class converts a java image to a PNG image and writes it to a specified output stream. It is compatible with JDK 1.1 and later.

The encoder supports 8 bit indexed images with 256 colors, 16 bit grayscale images and 24 bit RGB images. Full alpha channel is supported for truecolor and grayscale images while indexed images can only contain fully opaque or fully transparent pixels. Indexed images are generally smaller in size than truecolor and grayscale images.

    FileOutputStream out = new FileOutputStream("image.png");
    PngEncoder encoder = new PngEncoder();
    encoder.encode(image,out);
 

Version: 2.0

Author:

Bjorn J. Kvande., Philipp Kolibaba.

Field Summary

static int	BEST_COMPRESSION The best compression level.
static int	BEST_SPEED The compression level with the best speed.
static int	COLOR_GRAYSCALE Encode the image as 16bit grayscale image.
static int	COLOR_GRAYSCALE_ALPHA Encode the image as 16bit grayscale image with alpha.
static int	COLOR_INDEXED Encode the image as a palette indexed image with maximum 256 colors.
static int	COLOR_INDEXED_ALPHA Encode the image as a palette indexed image with maximum 256 colors.
static int	COLOR_TRUECOLOR Encode the image as 24bit truecolor RGB image with 16,7 million colors.
static int	COLOR_TRUECOLOR_ALPHA Encode the image as 24bit truecolor image with alpha.
static int	DEFAULT_COMPRESSION The default compression level.
static int	INDEXED_COLORS_AUTO The PngEncoder checks automatically if it should use original colors or convert to the pre-set palette.
static int	INDEXED_COLORS_CONVERT The original colors are used for the indexed PNG output.
static int	INDEXED_COLORS_ORIGINAL The original colors are converted to the pre-set palette.

Constructor Summary

PngEncoder()
Creates a new PngEncoder for truecolor images and default compression.

PngEncoder(int colorType)
Creates a new PngEncoder with the specified color type and default compression.

PngEncoder(int colorType, int compression)
Creates a new PngEncoder with the specified color type and compression.

Method Summary

void	encode(java.awt.Image image, java.io.OutputStream out) Encodes an image to an output stream as a PNG image.
int	getColorType() Gets the current image type.
int	getIndexedColorMode() Gets current mode of processing original image to indexed PNG.
static java.lang.String	getVersion() Gets the version number.
static void	main(java.lang.String[] argv) Prints out the version number.
void	setColorType(int colorType) Sets the encoded image type.
void	setCompression(int level) Sets the image compression level.
void	setIndexedColorMode(int mode) Sets mode to process the original image to indexed PNG output.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BEST_COMPRESSION

public static final int BEST_COMPRESSION

The best compression level.

See Also:

Constant Field Values

BEST_SPEED

public static final int BEST_SPEED

The compression level with the best speed.

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Constant Field Values

COLOR_GRAYSCALE

public static final int COLOR_GRAYSCALE

Encode the image as 16bit grayscale image.

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Constant Field Values

COLOR_GRAYSCALE_ALPHA

public static final int COLOR_GRAYSCALE_ALPHA

Encode the image as 16bit grayscale image with alpha.

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Constant Field Values

COLOR_INDEXED

public static final int COLOR_INDEXED

Encode the image as a palette indexed image with maximum 256 colors. This image type takes less space and is sometimes more efficiently encoded.

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Constant Field Values

COLOR_INDEXED_ALPHA

public static final int COLOR_INDEXED_ALPHA

Encode the image as a palette indexed image with maximum 256 colors.

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Constant Field Values

COLOR_TRUECOLOR

public static final int COLOR_TRUECOLOR

Encode the image as 24bit truecolor RGB image with 16,7 million colors.

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Constant Field Values

COLOR_TRUECOLOR_ALPHA

public static final int COLOR_TRUECOLOR_ALPHA

Encode the image as 24bit truecolor image with alpha.

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Constant Field Values

DEFAULT_COMPRESSION

public static final int DEFAULT_COMPRESSION

The default compression level.

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Constant Field Values

INDEXED_COLORS_AUTO

public static final int INDEXED_COLORS_AUTO

The PngEncoder checks automatically if it should use original colors or convert to the pre-set palette. Should be used when it is unknow if there is more or less then 256 colors in original image. Encoding in this mode might take more time then in other ones. This is the default mode.

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Constant Field Values

INDEXED_COLORS_CONVERT

public static final int INDEXED_COLORS_CONVERT

The original colors are used for the indexed PNG output. Should be set when there is less then 256 colors in original image.

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Constant Field Values

INDEXED_COLORS_ORIGINAL

public static final int INDEXED_COLORS_ORIGINAL

The original colors are converted to the pre-set palette. Should be used when there is more then 256 colors in originalimage

See Also:

Constant Field Values

Constructor Detail

PngEncoder

public PngEncoder()

Creates a new PngEncoder for truecolor images and default compression.

PngEncoder

public PngEncoder(int colorType)

Creates a new PngEncoder with the specified color type and default compression.

Parameters:

colorType - COLOR_TRUECOLOR, COLOR_INDEXED or COLOR_GRAYSCALE.

Throws:

java.lang.IllegalArgumentException - If the color type is invalid.

PngEncoder

public PngEncoder(int colorType,
                  int compression)

Creates a new PngEncoder with the specified color type and compression. The less compression, the faster the encoding will be and larger the image.

Parameters:

colorType - COLOR_TRUECOLOR, COLOR_INDEXED, COLOR_GRAYSCALE, COLOR_TRUECOLOR_ALPHA, COLOR_INDEXED_ALPHA, COLOR_GRAYSCALE_ALPHA.

compression - The compression level (0-9 or DEFAULT_COMPRESSION, BEST_SPEED, BEST_COMPRESSION).

Method Detail

encode

public void encode(java.awt.Image image,
                   java.io.OutputStream out)
            throws java.io.IOException

Encodes an image to an output stream as a PNG image. It does not close the output stream, this must be done by the caller.

Parameters:

image - the buffered image to encode.

out - the output stream to write the encoded data to.

Throws:

java.io.IOException

getColorType

public int getColorType()

Gets the current image type.

Returns:

COLOR_INDEXED, COLOR_TRUECOLOR or COLOR_GRAYSCALE.

getIndexedColorMode

public int getIndexedColorMode()

Gets current mode of processing original image to indexed PNG.

Returns:

Returns current

getVersion

public static java.lang.String getVersion()

Gets the version number.

main

public static void main(java.lang.String[] argv)

Prints out the version number.

setColorType

public void setColorType(int colorType)

Sets the encoded image type. Palette indexed images are smaller but can contain a maximum of 256 colors. Truecolor images uses one byte per pixel and can contain 16,7 million colors, but are larger.

Parameters:

colorType - COLOR_INDEXED, COLOR_TRUECOLOR or COLOR_GRAYSCALE.

Throws:

java.lang.IllegalArgumentException - If the color type is invalid.

setCompression

public void setCompression(int level)

Sets the image compression level. The better the compression the smaller the image and longer the encoding time.

Parameters:

level - 0-9 or DEFAULT_COMPRESSION, BEST_SPEED, or BEST_COMPRESSION.

Throws:

java.lang.IllegalArgumentException - If the compression level is invalid.

setIndexedColorMode

public void setIndexedColorMode(int mode)

Sets mode to process the original image to indexed PNG output.

Parameters:

mode - One of the following: INDEXED_COLORS_AUTO, INDEXED_COLORS_ORIGINAL, INDEXED_COLORS_CONVERT.