org.eclipse.swt.internal.image

Class PNGFileFormat

java.lang.Object

org.eclipse.swt.internal.image.FileFormat

org.eclipse.swt.internal.image.PNGFileFormat

public final class PNGFileFormat
extends FileFormat

Structure Diagram

Field Summary

Fields

Modifier and Type	Field and Description
(package private) int	adler
(package private) byte[]	alphaPalette
(package private) byte[]	data
(package private) byte	headerByte1
(package private) byte	headerByte2
(package private) PngIhdrChunk	headerChunk
(package private) ImageData	imageData
(package private) PngPlteChunk	paletteChunk
(package private) static int	PRIME
(package private) static int	SIGNATURE_LENGTH

Fields inherited from class org.eclipse.swt.internal.image.FileFormat

compression, FORMAT_PACKAGE, FORMAT_SUFFIX, FORMATS, inputStream, loader, outputStream

Constructor Summary

Constructors

Constructor and Description
PNGFileFormat()

Method Summary

Methods

Modifier and Type	Method and Description
(package private) static void	compress16BitDepthTo8BitDepth(byte[] source, int sourceOffset, byte[] destination, int destinationOffset, int numberOfValues) SWT does not support 16-bit depth color formats.
(package private) static int	compress16BitDepthTo8BitDepth(int value) SWT does not support 16-bit depth color formats.
(package private) void	filterRow(byte[] row, byte[] previousRow, int filterType) PNG supports four filtering types.
(package private) void	fireInterlacedFrameEvent(int frameCount) Fire an event to let listeners know that an interlaced frame has been loaded.
(package private) int	getAlignedBytesPerRow() Answer the number of bytes in a word-aligned row of pixel data.
(package private) int	getBytesPerPixel() Answer the number of bytes needed to represent a pixel.
(package private) int	getBytesPerRow() Answer the number of bytes in each row of the image data.
(package private) int	getBytesPerRow(int rowWidthInPixels) Answer the number of bytes in a row of the given pixel width.
(package private) boolean	isFileFormat(LEDataInputStream stream) Return whether or not the specified input stream represents a supported file format.
(package private) ImageData[]	loadFromByteStream() Load the PNG image from the byte stream.
(package private) void	readInterlacedImage(java.io.InputStream inputStream) Read the pixel data for an interlaced image from the data stream.
(package private) void	readInterlaceFrame(java.io.InputStream inputStream, int rowInterval, int columnInterval, int startRow, int startColumn, int frameCount) 1.
(package private) void	readNextChunk(PngChunkReader chunkReader) Read and handle the next chunk of data from the PNG file.
(package private) void	readNonInterlacedImage(java.io.InputStream inputStream) Read the pixel data for a non-interlaced image from the data stream.
(package private) void	readPixelData(PngIdatChunk chunk, PngChunkReader chunkReader) Read the image data from the data stream.
(package private) void	readSignature() Skip over signature data.
(package private) void	setImageDataValues(byte[] data, ImageData imageData) PNG supports some color types and bit depths that are unsupported by SWT.
(package private) void	setPixelData(byte[] data, ImageData imageData) SWT does not support greyscale as a color type.
(package private) void	unloadIntoByteStream(ImageLoader loader)
(package private) byte[]	validateBitDepth(byte[] data) SWT does not support 16-bit depths.

Methods inherited from class org.eclipse.swt.internal.image.FileFormat

load, loadFromStream, save, unloadIntoStream

Methods inherited from class java.lang.Object

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

Field Detail

SIGNATURE_LENGTH

static final int SIGNATURE_LENGTH

See Also:

Constant Field Values

PRIME

static final int PRIME

See Also:

Constant Field Values

headerChunk

PngIhdrChunk headerChunk

paletteChunk

PngPlteChunk paletteChunk

imageData

ImageData imageData

data

byte[] data

alphaPalette

byte[] alphaPalette

headerByte1

byte headerByte1

headerByte2

byte headerByte2

adler

int adler

Constructor Detail

PNGFileFormat

public PNGFileFormat()

Method Detail

readSignature

void readSignature()
             throws java.io.IOException

Skip over signature data. This has already been verified in isFileFormat().

Throws:

java.io.IOException

loadFromByteStream

ImageData[] loadFromByteStream()

Load the PNG image from the byte stream.

Specified by:

loadFromByteStream in class FileFormat

readNextChunk

void readNextChunk(PngChunkReader chunkReader)
             throws java.io.IOException

Read and handle the next chunk of data from the PNG file.

Throws:

java.io.IOException

unloadIntoByteStream

void unloadIntoByteStream(ImageLoader loader)

Specified by:

unloadIntoByteStream in class FileFormat

isFileFormat

boolean isFileFormat(LEDataInputStream stream)

Description copied from class: FileFormat

Return whether or not the specified input stream represents a supported file format.

Specified by:

isFileFormat in class FileFormat

validateBitDepth

byte[] validateBitDepth(byte[] data)

SWT does not support 16-bit depths. If this image uses 16-bit depths, convert the data to an 8-bit depth.

setPixelData

void setPixelData(byte[] data,
                ImageData imageData)

SWT does not support greyscale as a color type. For plain grayscale, we create a palette. For Grayscale with Alpha, however, we need to convert the pixels to use RGB values. Note: This method assumes that the bit depth of the data has already been restricted to 8 or less.

setImageDataValues

void setImageDataValues(byte[] data,
                      ImageData imageData)

PNG supports some color types and bit depths that are unsupported by SWT. If the image uses an unsupported color type (either of the gray scale types) or bit depth (16), convert the data to an SWT-supported format. Then assign the data into the ImageData given.

readPixelData

void readPixelData(PngIdatChunk chunk,
                 PngChunkReader chunkReader)
             throws java.io.IOException

Read the image data from the data stream. This must handle decoding the data, filtering, and interlacing.

Throws:

java.io.IOException

getAlignedBytesPerRow

int getAlignedBytesPerRow()

Answer the number of bytes in a word-aligned row of pixel data.

getBytesPerRow

int getBytesPerRow()

Answer the number of bytes in each row of the image data. Each PNG row is byte-aligned, so images with bit depths less than a byte may have unused bits at the end of each row. The value of these bits is undefined.

getBytesPerPixel

int getBytesPerPixel()

Answer the number of bytes needed to represent a pixel. This value depends on the image's color type and bit depth. Note that this method rounds up if an image's pixel size isn't byte-aligned.

getBytesPerRow

int getBytesPerRow(int rowWidthInPixels)

Answer the number of bytes in a row of the given pixel width. Each row is byte-aligned, so images with bit depths less than a byte may have unused bits at the end of each row. The value of these bits is undefined.

readInterlaceFrame

void readInterlaceFrame(java.io.InputStream inputStream,
                      int rowInterval,
                      int columnInterval,
                      int startRow,
                      int startColumn,
                      int frameCount)
                  throws java.io.IOException

1. Read one of the seven frames of interlaced data. 2. Update the imageData. 3. Notify the image loader's listeners of the frame load.

Throws:

java.io.IOException

readInterlacedImage

void readInterlacedImage(java.io.InputStream inputStream)
                   throws java.io.IOException

Read the pixel data for an interlaced image from the data stream.

Throws:

java.io.IOException

fireInterlacedFrameEvent

void fireInterlacedFrameEvent(int frameCount)

Fire an event to let listeners know that an interlaced frame has been loaded. finalFrame should be true if the image has finished loading, false if there are more frames to come.

readNonInterlacedImage

void readNonInterlacedImage(java.io.InputStream inputStream)
                      throws java.io.IOException

Read the pixel data for a non-interlaced image from the data stream. Update the imageData to reflect the new data.

Throws:

java.io.IOException

compress16BitDepthTo8BitDepth

static void compress16BitDepthTo8BitDepth(byte[] source,
                                 int sourceOffset,
                                 byte[] destination,
                                 int destinationOffset,
                                 int numberOfValues)

SWT does not support 16-bit depth color formats. Convert the 16-bit data to 8-bit data. The correct way to do this is to multiply each 16 bit value by the value: (2^8 - 1) / (2^16 - 1). The fast way to do this is just to drop the low byte of the 16-bit value.

compress16BitDepthTo8BitDepth

static int compress16BitDepthTo8BitDepth(int value)

SWT does not support 16-bit depth color formats. Convert the 16-bit data to 8-bit data. The correct way to do this is to multiply each 16 bit value by the value: (2^8 - 1) / (2^16 - 1). The fast way to do this is just to drop the low byte of the 16-bit value.

filterRow

void filterRow(byte[] row,
             byte[] previousRow,
             int filterType)

PNG supports four filtering types. These types are applied per row of image data. This method unfilters the given row based on the filterType.