Java tutorial
/* * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.imageio; import java.awt.Dimension; import java.awt.image.BufferedImage; /** * A class describing how a stream is to be decoded. Instances of * this class or its subclasses are used to supply prescriptive * "how-to" information to instances of {@code ImageReader}. * * <p> An image encoded as part of a file or stream may be thought of * extending out in multiple dimensions: the spatial dimensions of * width and height, a number of bands, and a number of progressive * decoding passes. This class allows a contiguous (hyper)rectangular * subarea of the image in all of these dimensions to be selected for * decoding. Additionally, the spatial dimensions may be subsampled * discontinuously. Finally, color and format conversions may be * specified by controlling the {@code ColorModel} and * {@code SampleModel} of the destination image, either by * providing a {@code BufferedImage} or by using an * {@code ImageTypeSpecifier}. * * <p> An {@code ImageReadParam} object is used to specify how an * image, or a set of images, will be converted on input from * a stream in the context of the Java Image I/O framework. A plug-in for a * specific image format will return instances of * {@code ImageReadParam} from the * {@code getDefaultReadParam} method of its * {@code ImageReader} implementation. * * <p> The state maintained by an instance of * {@code ImageReadParam} is independent of any particular image * being decoded. When actual decoding takes place, the values set in * the read param are combined with the actual properties of the image * being decoded from the stream and the destination * {@code BufferedImage} that will receive the decoded pixel * data. For example, the source region set using * {@code setSourceRegion} will first be intersected with the * actual valid source area. The result will be translated by the * value returned by {@code getDestinationOffset}, and the * resulting rectangle intersected with the actual valid destination * area to yield the destination area that will be written. * * <p> The parameters specified by an {@code ImageReadParam} are * applied to an image as follows. First, if a rendering size has * been set by {@code setSourceRenderSize}, the entire decoded * image is rendered at the size given by * {@code getSourceRenderSize}. Otherwise, the image has its * natural size given by {@code ImageReader.getWidth} and * {@code ImageReader.getHeight}. * * <p> Next, the image is clipped against the source region * specified by {@code getSourceXOffset}, {@code getSourceYOffset}, * {@code getSourceWidth}, and {@code getSourceHeight}. * * <p> The resulting region is then subsampled according to the * factors given in {@link IIOParam#setSourceSubsampling * IIOParam.setSourceSubsampling}. The first pixel, * the number of pixels per row, and the number of rows all depend * on the subsampling settings. * Call the minimum X and Y coordinates of the resulting rectangle * ({@code minX}, {@code minY}), its width {@code w} * and its height {@code h}. * * <p> This rectangle is offset by * ({@code getDestinationOffset().x}, * {@code getDestinationOffset().y}) and clipped against the * destination bounds. If no destination image has been set, the * destination is defined to have a width of * {@code getDestinationOffset().x} + {@code w}, and a * height of {@code getDestinationOffset().y} + {@code h} so * that all pixels of the source region may be written to the * destination. * * <p> Pixels that land, after subsampling, within the destination * image, and that are written in one of the progressive passes * specified by {@code getSourceMinProgressivePass} and * {@code getSourceNumProgressivePasses} are passed along to the * next step. * * <p> Finally, the source samples of each pixel are mapped into * destination bands according to the algorithm described in the * comment for {@code setDestinationBands}. * * <p> Plug-in writers may extend the functionality of * {@code ImageReadParam} by providing a subclass that implements * additional, plug-in specific interfaces. It is up to the plug-in * to document what interfaces are available and how they are to be * used. Readers will silently ignore any extended features of an * {@code ImageReadParam} subclass of which they are not aware. * Also, they may ignore any optional features that they normally * disable when creating their own {@code ImageReadParam} * instances via {@code getDefaultReadParam}. * * <p> Note that unless a query method exists for a capability, it must * be supported by all {@code ImageReader} implementations * (<i>e.g.</i> source render size is optional, but subsampling must be * supported). * * * @see ImageReader * @see ImageWriter * @see ImageWriteParam */ public class ImageReadParam extends IIOParam { /** * {@code true} if this {@code ImageReadParam} allows * the source rendering dimensions to be set. By default, the * value is {@code false}. Subclasses must set this value * manually. * * <p> {@code ImageReader}s that do not support setting of * the source render size should set this value to * {@code false}. */ protected boolean canSetSourceRenderSize = false; /** * The desired rendering width and height of the source, if * {@code canSetSourceRenderSize} is {@code true}, or * {@code null}. * * <p> {@code ImageReader}s that do not support setting of * the source render size may ignore this value. */ protected Dimension sourceRenderSize = null; /** * The current destination {@code BufferedImage}, or * {@code null} if none has been set. By default, the value * is {@code null}. */ protected BufferedImage destination = null; /** * The set of destination bands to be used, as an array of * {@code int}s. By default, the value is {@code null}, * indicating all destination bands should be written in order. */ protected int[] destinationBands = null; /** * The minimum index of a progressive pass to read from the * source. By default, the value is set to 0, which indicates * that passes starting with the first available pass should be * decoded. * * <p> Subclasses should ensure that this value is * non-negative. */ protected int minProgressivePass = 0; /** * The maximum number of progressive passes to read from the * source. By default, the value is set to * {@code Integer.MAX_VALUE}, which indicates that passes up * to and including the last available pass should be decoded. * * <p> Subclasses should ensure that this value is positive. * Additionally, if the value is not * {@code Integer.MAX_VALUE}, then * {@code minProgressivePass + numProgressivePasses - 1} * should not exceed * {@code Integer.MAX_VALUE}. */ protected int numProgressivePasses = Integer.MAX_VALUE; /** * Constructs an {@code ImageReadParam}. */ public ImageReadParam() { } // Comment inherited public void setDestinationType(ImageTypeSpecifier destinationType) { super.setDestinationType(destinationType); setDestination(null); } /** * Supplies a {@code BufferedImage} to be used as the * destination for decoded pixel data. The currently set image * will be written to by the {@code read}, * {@code readAll}, and {@code readRaster} methods, and * a reference to it will be returned by those methods. * * <p> Pixel data from the aforementioned methods will be written * starting at the offset specified by * {@code getDestinationOffset}. * * <p> If {@code destination} is {@code null}, a * newly-created {@code BufferedImage} will be returned by * those methods. * * <p> At the time of reading, the image is checked to verify that * its {@code ColorModel} and {@code SampleModel} * correspond to one of the {@code ImageTypeSpecifier}s * returned from the {@code ImageReader}'s * {@code getImageTypes} method. If it does not, the reader * will throw an {@code IIOException}. * * @param destination the BufferedImage to be written to, or * {@code null}. * * @see #getDestination */ public void setDestination(BufferedImage destination) { this.destination = destination; } /** * Returns the {@code BufferedImage} currently set by the * {@code setDestination} method, or {@code null} * if none is set. * * @return the BufferedImage to be written to. * * @see #setDestination */ public BufferedImage getDestination() { return destination; } /** * Sets the indices of the destination bands where data * will be placed. Duplicate indices are not allowed. * * <p> A {@code null} value indicates that all destination * bands will be used. * * <p> Choosing a destination band subset will not affect the * number of bands in the output image of a read if no destination * image is specified; the created destination image will still * have the same number of bands as if this method had never been * called. If a different number of bands in the destination * image is desired, an image must be supplied using the * {@code ImageReadParam.setDestination} method. * * <p> At the time of reading or writing, an * {@code IllegalArgumentException} will be thrown by the * reader or writer if a value larger than the largest destination * band index has been specified, or if the number of source bands * and destination bands to be used differ. The * {@code ImageReader.checkReadParamBandSettings} method may * be used to automate this test. * * @param destinationBands an array of integer band indices to be * used. * * @exception IllegalArgumentException if {@code destinationBands} * contains a negative or duplicate value. * * @see #getDestinationBands * @see #getSourceBands * @see ImageReader#checkReadParamBandSettings */ public void setDestinationBands(int[] destinationBands) { if (destinationBands == null) { this.destinationBands = null; } else { int numBands = destinationBands.length; for (int i = 0; i < numBands; i++) { int band = destinationBands[i]; if (band < 0) { throw new IllegalArgumentException("Band value < 0!"); } for (int j = i + 1; j < numBands; j++) { if (band == destinationBands[j]) { throw new IllegalArgumentException("Duplicate band value!"); } } } this.destinationBands = destinationBands.clone(); } } /** * Returns the set of band indices where data will be placed. * If no value has been set, {@code null} is returned to * indicate that all destination bands will be used. * * @return the indices of the destination bands to be used, * or {@code null}. * * @see #setDestinationBands */ public int[] getDestinationBands() { if (destinationBands == null) { return null; } else { return destinationBands.clone(); } } /** * Returns {@code true} if this reader allows the source * image to be rendered at an arbitrary size as part of the * decoding process, by means of the * {@code setSourceRenderSize} method. If this method * returns {@code false}, calls to * {@code setSourceRenderSize} will throw an * {@code UnsupportedOperationException}. * * @return {@code true} if setting source rendering size is * supported. * * @see #setSourceRenderSize */ public boolean canSetSourceRenderSize() { return canSetSourceRenderSize; } /** * If the image is able to be rendered at an arbitrary size, sets * the source width and height to the supplied values. Note that * the values returned from the {@code getWidth} and * {@code getHeight} methods on {@code ImageReader} are * not affected by this method; they will continue to return the * default size for the image. Similarly, if the image is also * tiled the tile width and height are given in terms of the default * size. * * <p> Typically, the width and height should be chosen such that * the ratio of width to height closely approximates the aspect * ratio of the image, as returned from * {@code ImageReader.getAspectRatio}. * * <p> If this plug-in does not allow the rendering size to be * set, an {@code UnsupportedOperationException} will be * thrown. * * <p> To remove the render size setting, pass in a value of * {@code null} for {@code size}. * * @param size a {@code Dimension} indicating the desired * width and height. * * @exception IllegalArgumentException if either the width or the * height is negative or 0. * @exception UnsupportedOperationException if image resizing * is not supported by this plug-in. * * @see #getSourceRenderSize * @see ImageReader#getWidth * @see ImageReader#getHeight * @see ImageReader#getAspectRatio */ public void setSourceRenderSize(Dimension size) throws UnsupportedOperationException { if (!canSetSourceRenderSize()) { throw new UnsupportedOperationException("Can't set source render size!"); } if (size == null) { this.sourceRenderSize = null; } else { if (size.width <= 0 || size.height <= 0) { throw new IllegalArgumentException("width or height <= 0!"); } this.sourceRenderSize = (Dimension) size.clone(); } } /** * Returns the width and height of the source image as it * will be rendered during decoding, if they have been set via the * {@code setSourceRenderSize} method. A * {@code null} value indicates that no setting has been made. * * @return the rendered width and height of the source image * as a {@code Dimension}. * * @see #setSourceRenderSize */ public Dimension getSourceRenderSize() { return (sourceRenderSize == null) ? null : (Dimension) sourceRenderSize.clone(); } /** * Sets the range of progressive passes that will be decoded. * Passes outside of this range will be ignored. * * <p> A progressive pass is a re-encoding of the entire image, * generally at progressively higher effective resolutions, but * requiring greater transmission bandwidth. The most common use * of progressive encoding is found in the JPEG format, where * successive passes include more detailed representations of the * high-frequency image content. * * <p> The actual number of passes to be decoded is determined * during decoding, based on the number of actual passes available * in the stream. Thus if {@code minPass + numPasses - 1} is * larger than the index of the last available passes, decoding * will end with that pass. * * <p> A value of {@code numPasses} of * {@code Integer.MAX_VALUE} indicates that all passes from * {@code minPass} forward should be read. Otherwise, the * index of the last pass (<i>i.e.</i>, {@code minPass + numPasses - 1}) * must not exceed {@code Integer.MAX_VALUE}. * * <p> There is no {@code unsetSourceProgressivePasses} * method; the same effect may be obtained by calling * {@code setSourceProgressivePasses(0, Integer.MAX_VALUE)}. * * @param minPass the index of the first pass to be decoded. * @param numPasses the maximum number of passes to be decoded. * * @exception IllegalArgumentException if {@code minPass} is * negative, {@code numPasses} is negative or 0, or * {@code numPasses} is smaller than * {@code Integer.MAX_VALUE} but * {@code minPass + numPasses - 1} is greater than * {@code INTEGER.MAX_VALUE}. * * @see #getSourceMinProgressivePass * @see #getSourceMaxProgressivePass */ public void setSourceProgressivePasses(int minPass, int numPasses) { if (minPass < 0) { throw new IllegalArgumentException("minPass < 0!"); } if (numPasses <= 0) { throw new IllegalArgumentException("numPasses <= 0!"); } if ((numPasses != Integer.MAX_VALUE) && (((minPass + numPasses - 1) & 0x80000000) != 0)) { throw new IllegalArgumentException("minPass + numPasses - 1 > INTEGER.MAX_VALUE!"); } this.minProgressivePass = minPass; this.numProgressivePasses = numPasses; } /** * Returns the index of the first progressive pass that will be * decoded. If no value has been set, 0 will be returned (which is * the correct value). * * @return the index of the first pass that will be decoded. * * @see #setSourceProgressivePasses * @see #getSourceNumProgressivePasses */ public int getSourceMinProgressivePass() { return minProgressivePass; } /** * If {@code getSourceNumProgressivePasses} is equal to * {@code Integer.MAX_VALUE}, returns * {@code Integer.MAX_VALUE}. Otherwise, returns * {@code getSourceMinProgressivePass() + * getSourceNumProgressivePasses() - 1}. * * @return the index of the last pass to be read, or * {@code Integer.MAX_VALUE}. */ public int getSourceMaxProgressivePass() { if (numProgressivePasses == Integer.MAX_VALUE) { return Integer.MAX_VALUE; } else { return minProgressivePass + numProgressivePasses - 1; } } /** * Returns the number of the progressive passes that will be * decoded. If no value has been set, * {@code Integer.MAX_VALUE} will be returned (which is the * correct value). * * @return the number of the passes that will be decoded. * * @see #setSourceProgressivePasses * @see #getSourceMinProgressivePass */ public int getSourceNumProgressivePasses() { return numProgressivePasses; } }