如何在不使用Swing API的情况下保存JAVA FX图表？
我有以下功能来保存LineChart图像：
@FXML
public void saveAsPng() {
String timeStamp = new SimpleDateFormat("HHmmss_yyyyMMdd").format(Calendar.getInstance().getTime());
chart.setAnimated(false);
System.out.println("Saving . . .");
WritableImage image = chart.snapshot(new SnapshotParameters(), null);
File file = new File("chart"+timeStamp+".png");
try {
ImageIO.write(SwingFXUtils.fromFXImage(image, null), "png", file);
} catch (IOException e) {
Logger.getLogger(SampleController.class.getName()).log(Level.SEVERE, null, e);
System.out.println("Error");
}
}
可悲的是，ARM的JDK支持 Swing API 。 我在使用时遇到错误：
ImageIO.write(SwingFXUtils.fromFXImage(image, null), "png", file);
我在 WritableImage图像变量中有渲染图像。有没有其他方法可以保存图表？
1 个答案:
答案 0 :(得分：4)
建议的方法
PNG编码非常简单。谷歌一些基于Java的png实现并修改它们的源代码，使用JavaFX PixelReader来输入像素数据而不是awt图像。
以下是您可以修改的示例项目：
http://catcode.com/pngencoder/
请务必检查您修改的实施的任何许可要求。
示例解决方案
我认为我会尝试一下这个实现起来非常微不足道（感谢catcode中的png编码源，我之前发现并链接过）。
下面的代码绝对没有断言它会做你想要的。我所做的就是删除AWT图像和像素抓取器引用，并用JavaFX图像和像素阅读器引用替换它们。但它似乎适用于我尝试的有限测试用例。
示例输出
左侧的图像是原始图表。右侧的图像是导出的PNG编码图表，加载回JavaFX并显示在ImageView中。
左边的图像更清晰，可能是因为我在视网膜上进行了开发，因此需要以双像素分辨率保存图像，以便在导出的图像中获得与源相同的保真度。
场景根有叶子的背景图像。图表使用半透明的彩色背景，以便显示背景 - 这可确保alpha编码适用于生成的png文件。
PngEncoderFX.java - 用于JavaFX图像的Png编码器
import javafx.scene.image.Image;
import javafx.scene.image.PixelFormat;
import javafx.scene.image.PixelReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
/**
* PngEncoder takes a Java Image object and creates a byte string which can be saved as a PNG file.
* The Image is presumed to use the DirectColorModel.
*
* <p>Thanks to Jay Denny at KeyPoint Software
* http://www.keypoint.com/
* who let me develop this code on company time.</p>
*
* <p>You may contact me with (probably very-much-needed) improvements,
* comments, and bug fixes at:</p>
*
* <p><code>david@catcode.com</code></p>
*
* <p>This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.</p>
*
* <p>This library 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
* Lesser General Public License for more details.</p>
*
* <p>You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
* A copy of the GNU LGPL may be found at
* <code>http://www.gnu.org/copyleft/lesser.html</code></p>
*
* @author J. David Eisenberg
* @version 1.5, 19 Oct 2003
*
* CHANGES:
* --------
* 30-Jav-2015 : Hacked source to work with JavaFX images instead of AWT images (by Jewelsea for StackOverflow).
* 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object Refinery Limited);
* 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
* 19-Oct-2003 : Change private fields to protected fields so that
* PngEncoderB can inherit them (JDE)
* Fixed bug with calculation of nRows
*/
public class PngEncoderFX extends Object {
/** Constant specifying that alpha channel should be encoded. */
public static final boolean ENCODE_ALPHA = true;
/** Constant specifying that alpha channel should not be encoded. */
public static final boolean NO_ALPHA = false;
/** Constants for filter (NONE) */
public static final int FILTER_NONE = 0;
/** Constants for filter (SUB) */
public static final int FILTER_SUB = 1;
/** Constants for filter (UP) */
public static final int FILTER_UP = 2;
/** Constants for filter (LAST) */
public static final int FILTER_LAST = 2;
/** IHDR tag. */
protected static final byte IHDR[] = {73, 72, 68, 82};
/** IDAT tag. */
protected static final byte IDAT[] = {73, 68, 65, 84};
/** IEND tag. */
protected static final byte IEND[] = {73, 69, 78, 68};
/** The png bytes. */
protected byte[] pngBytes;
/** The prior row. */
protected byte[] priorRow;
/** The left bytes. */
protected byte[] leftBytes;
/** The image. */
protected Image image;
/** The width. */
protected int width, height;
/** The byte position. */
protected int bytePos, maxPos;
/** CRC. */
protected CRC32 crc = new CRC32();
/** The CRC value. */
protected long crcValue;
/** Encode alpha? */
protected boolean encodeAlpha;
/** The filter type. */
protected int filter;
/** The bytes-per-pixel. */
protected int bytesPerPixel;
/** The compression level. */
protected int compressionLevel;
/**
* Class constructor
*/
public PngEncoderFX() {
this(null, false, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, with no alpha channel encoding.
*
* @param image A Java Image object which uses the DirectColorModel
* @see java.awt.Image
*/
public PngEncoderFX(Image image) {
this(image, false, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, and whether to encode alpha.
*
* @param image A Java Image object which uses the DirectColorModel
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @see java.awt.Image
*/
public PngEncoderFX(Image image, boolean encodeAlpha) {
this(image, encodeAlpha, FILTER_NONE, 0);
}
/**
* Class constructor specifying Image to encode, whether to encode alpha, and filter to use.
*
* @param image A Java Image object which uses the DirectColorModel
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @param whichFilter 0=none, 1=sub, 2=up
* @see java.awt.Image
*/
public PngEncoderFX(Image image, boolean encodeAlpha, int whichFilter) {
this(image, encodeAlpha, whichFilter, 0);
}
/**
* Class constructor specifying Image source to encode, whether to encode alpha, filter to use,
* and compression level.
*
* @param image A Java Image object
* @param encodeAlpha Encode the alpha channel? false=no; true=yes
* @param whichFilter 0=none, 1=sub, 2=up
* @param compLevel 0..9
* @see java.awt.Image
*/
public PngEncoderFX(Image image, boolean encodeAlpha, int whichFilter, int compLevel) {
this.image = image;
this.encodeAlpha = encodeAlpha;
setFilter(whichFilter);
if (compLevel >= 0 && compLevel <= 9) {
this.compressionLevel = compLevel;
}
}
/**
* Set the image to be encoded
*
* @param image A Java Image object which uses the DirectColorModel
* @see java.awt.Image
* @see java.awt.image.DirectColorModel
*/
public void setImage(Image image) {
this.image = image;
pngBytes = null;
}
/**
* Creates an array of bytes that is the PNG equivalent of the current image, specifying
* whether to encode alpha or not.
*
* @param encodeAlpha boolean false=no alpha, true=encode alpha
* @return an array of bytes, or null if there was a problem
*/
public byte[] pngEncode(boolean encodeAlpha) {
byte[] pngIdBytes = {-119, 80, 78, 71, 13, 10, 26, 10};
if (image == null) {
return null;
}
width = (int) image.getWidth();
height = (int) image.getHeight();
/*
* start with an array that is big enough to hold all the pixels
* (plus filter bytes), and an extra 200 bytes for header info
*/
pngBytes = new byte[((width + 1) * height * 3) + 200];
/*
* keep track of largest byte written to the array
*/
maxPos = 0;
bytePos = writeBytes(pngIdBytes, 0);
//hdrPos = bytePos;
writeHeader();
//dataPos = bytePos;
if (writeImageData()) {
writeEnd();
pngBytes = resizeByteArray(pngBytes, maxPos);
}
else {
pngBytes = null;
}
return pngBytes;
}
/**
* Creates an array of bytes that is the PNG equivalent of the current image.
* Alpha encoding is determined by its setting in the constructor.
*
* @return an array of bytes, or null if there was a problem
*/
public byte[] pngEncode() {
return pngEncode(encodeAlpha);
}
/**
* Set the alpha encoding on or off.
*
* @param encodeAlpha false=no, true=yes
*/
public void setEncodeAlpha(boolean encodeAlpha) {
this.encodeAlpha = encodeAlpha;
}
/**
* Retrieve alpha encoding status.
*
* @return boolean false=no, true=yes
*/
public boolean getEncodeAlpha() {
return encodeAlpha;
}
/**
* Set the filter to use
*
* @param whichFilter from constant list
*/
public void setFilter(int whichFilter) {
this.filter = FILTER_NONE;
if (whichFilter <= FILTER_LAST) {
this.filter = whichFilter;
}
}
/**
* Retrieve filtering scheme
*
* @return int (see constant list)
*/
public int getFilter() {
return filter;
}
/**
* Set the compression level to use
*
* @param level 0 through 9
*/
public void setCompressionLevel(int level) {
if (level >= 0 && level <= 9) {
this.compressionLevel = level;
}
}
/**
* Retrieve compression level
*
* @return int in range 0-9
*/
public int getCompressionLevel() {
return compressionLevel;
}
/**
* Increase or decrease the length of a byte array.
*
* @param array The original array.
* @param newLength The length you wish the new array to have.
* @return Array of newly desired length. If shorter than the
* original, the trailing elements are truncated.
*/
protected byte[] resizeByteArray(byte[] array, int newLength) {
byte[] newArray = new byte[newLength];
int oldLength = array.length;
System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));
return newArray;
}
/**
* Write an array of bytes into the pngBytes array.
* Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes(byte[] data, int offset) {
maxPos = Math.max(maxPos, offset + data.length);
if (data.length + offset > pngBytes.length) {
pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, data.length));
}
System.arraycopy(data, 0, pngBytes, offset, data.length);
return offset + data.length;
}
/**
* Write an array of bytes into the pngBytes array, specifying number of bytes to write.
* Note: This routine has the side effect of updating
* maxPos, the largest element written in the array.
* The array is resized by 1000 bytes or the length
* of the data to be written, whichever is larger.
*
* @param data The data to be written into pngBytes.
* @param nBytes The number of bytes to be written.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeBytes(byte[] data, int nBytes, int offset) {
maxPos = Math.max(maxPos, offset + nBytes);
if (nBytes + offset > pngBytes.length) {
pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, nBytes));
}
System.arraycopy(data, 0, pngBytes, offset, nBytes);
return offset + nBytes;
}
/**
* Write a two-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt2(int n, int offset) {
byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};
return writeBytes(temp, offset);
}
/**
* Write a four-byte integer into the pngBytes array at a given position.
*
* @param n The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeInt4(int n, int offset) {
byte[] temp = {(byte) ((n >> 24) & 0xff),
(byte) ((n >> 16) & 0xff),
(byte) ((n >> 8) & 0xff),
(byte) (n & 0xff)};
return writeBytes(temp, offset);
}
/**
* Write a single byte into the pngBytes array at a given position.
*
* @param b The integer to be written into pngBytes.
* @param offset The starting point to write to.
* @return The next place to be written to in the pngBytes array.
*/
protected int writeByte(int b, int offset) {
byte[] temp = {(byte) b};
return writeBytes(temp, offset);
}
/**
* Write a PNG "IHDR" chunk into the pngBytes array.
*/
protected void writeHeader() {
int startPos;
startPos = bytePos = writeInt4(13, bytePos);
bytePos = writeBytes(IHDR, bytePos);
width = (int) image.getWidth();
height = (int) image.getHeight();
bytePos = writeInt4(width, bytePos);
bytePos = writeInt4(height, bytePos);
bytePos = writeByte(8, bytePos); // bit depth
bytePos = writeByte((encodeAlpha) ? 6 : 2, bytePos); // direct model
bytePos = writeByte(0, bytePos); // compression method
bytePos = writeByte(0, bytePos); // filter method
bytePos = writeByte(0, bytePos); // no interlace
crc.reset();
crc.update(pngBytes, startPos, bytePos - startPos);
crcValue = crc.getValue();
bytePos = writeInt4((int) crcValue, bytePos);
}
/**
* Perform "sub" filtering on the given row.
* Uses temporary array leftBytes to store the original values
* of the previous pixels. The array is 16 bytes long, which
* will easily hold two-byte samples plus two-byte alpha.
*
* @param pixels The array holding the scan lines being built
* @param startPos Starting position within pixels of bytes to be filtered.
* @param width Width of a scanline in pixels.
*/
protected void filterSub(byte[] pixels, int startPos, int width) {
int i;
int offset = bytesPerPixel;
int actualStart = startPos + offset;
int nBytes = width * bytesPerPixel;
int leftInsert = offset;
int leftExtract = 0;
for (i = actualStart; i < startPos + nBytes; i++) {
leftBytes[leftInsert] = pixels[i];
pixels[i] = (byte) ((pixels[i] - leftBytes[leftExtract]) % 256);
leftInsert = (leftInsert + 1) % 0x0f;
leftExtract = (leftExtract + 1) % 0x0f;
}
}
/**
* Perform "up" filtering on the given row.
* Side effect: refills the prior row with current row
*
* @param pixels The array holding the scan lines being built
* @param startPos Starting position within pixels of bytes to be filtered.
* @param width Width of a scanline in pixels.
*/
protected void filterUp(byte[] pixels, int startPos, int width) {
int i, nBytes;
byte currentByte;
nBytes = width * bytesPerPixel;
for (i = 0; i < nBytes; i++) {
currentByte = pixels[startPos + i];
pixels[startPos + i] = (byte) ((pixels[startPos + i] - priorRow[i]) % 256);
priorRow[i] = currentByte;
}
}
/**
* Write the image data into the pngBytes array.
* This will write one or more PNG "IDAT" chunks. In order
* to conserve memory, this method grabs as many rows as will
* fit into 32K bytes, or the whole image; whichever is less.
*
*
* @return true if no errors; false if error grabbing pixels
*/
protected boolean writeImageData() {
int rowsLeft = height; // number of rows remaining to write
int startRow = 0; // starting row to process this time through
int nRows; // how many rows to grab at a time
byte[] scanLines; // the scan lines to be compressed
int scanPos; // where we are in the scan lines
int startPos; // where this line's actual pixels start (used for filtering)
byte[] compressedLines; // the resultant compressed lines
int nCompressed; // how big is the compressed area?
//int depth; // color depth ( handle only 8 or 32 )
PixelReader pg = image.getPixelReader();
bytesPerPixel = (encodeAlpha) ? 4 : 3;
Deflater scrunch = new Deflater(compressionLevel);
ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);
DeflaterOutputStream compBytes = new DeflaterOutputStream(outBytes, scrunch);
try {
while (rowsLeft > 0) {
nRows = Math.min(32767 / (width * (bytesPerPixel + 1)), rowsLeft);
nRows = Math.max( nRows, 1 );
int[] pixels = new int[width * nRows];
pg.getPixels(0, startRow, width, nRows, PixelFormat.getIntArgbInstance(), pixels, 0, width);
/*
* Create a data chunk. scanLines adds "nRows" for
* the filter bytes.
*/
scanLines = new byte[width * nRows * bytesPerPixel + nRows];
if (filter == FILTER_SUB) {
leftBytes = new byte[16];
}
if (filter == FILTER_UP) {
priorRow = new byte[width * bytesPerPixel];
}
scanPos = 0;
startPos = 1;
for (int i = 0; i < width * nRows; i++) {
if (i % width == 0) {
scanLines[scanPos++] = (byte) filter;
startPos = scanPos;
}
scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);
scanLines[scanPos++] = (byte) ((pixels[i] >> 8) & 0xff);
scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);
if (encodeAlpha) {
scanLines[scanPos++] = (byte) ((pixels[i] >> 24) & 0xff);
}
if ((i % width == width - 1) && (filter != FILTER_NONE)) {
if (filter == FILTER_SUB) {
filterSub(scanLines, startPos, width);
}
if (filter == FILTER_UP) {
filterUp(scanLines, startPos, width);
}
}
}
/*
* Write these lines to the output area
*/
compBytes.write(scanLines, 0, scanPos);
startRow += nRows;
rowsLeft -= nRows;
}
compBytes.close();
/*
* Write the compressed bytes
*/
compressedLines = outBytes.toByteArray();
nCompressed = compressedLines.length;
crc.reset();
bytePos = writeInt4(nCompressed, bytePos);
bytePos = writeBytes(IDAT, bytePos);
crc.update(IDAT);
bytePos = writeBytes(compressedLines, nCompressed, bytePos);
crc.update(compressedLines, 0, nCompressed);
crcValue = crc.getValue();
bytePos = writeInt4((int) crcValue, bytePos);
scrunch.finish();
return true;
}
catch (IOException e) {
System.err.println(e.toString());
return false;
}
}
/**
* Write a PNG "IEND" chunk into the pngBytes array.
*/
protected void writeEnd() {
bytePos = writeInt4(0, bytePos);
bytePos = writeBytes(IEND, bytePos);
crc.reset();
crc.update(IEND);
crcValue = crc.getValue();
bytePos = writeInt4((int) crcValue, bytePos);
}
}
PieChartPngEncoder.java - 测试工具
import javafx.application.Application;
import javafx.collections.*;
import javafx.geometry.*;
import javafx.scene.*;
import javafx.scene.control.Label;
import javafx.scene.image.*;
import javafx.scene.layout.*;
import javafx.scene.paint.*;
import javafx.stage.Stage;
import javafx.scene.chart.*;
import java.io.IOException;
import java.nio.file.*;
import java.util.logging.*;
/**
* Demonstrates encoding a JavaFX node to a PNG image using a custom PNG encoder and no AWT/Swing classes.
*/
public class PieChartPngEncoder extends Application {
private static final Logger logger = Logger.getLogger(PieChartPngEncoder.class.getName());
@Override public void start(Stage stage) throws IOException {
final PieChart chart = createChart();
chart.getStylesheets().add(getClass().getResource(
"chart.css"
).toExternalForm());
chart.getStyleClass().add("translucent-background");
Path imagePath = Files.createTempFile("png-test", ".png");
exportPngSnapshot(
chart,
imagePath,
Color.TRANSPARENT
);
Image chartImage = new Image(
imagePath.toUri().toURL().toExternalForm()
);
Label exportLocation = new Label("Exported to " + imagePath);
exportLocation.setStyle("");
exportLocation.getStyleClass().add("overlay-label");
VBox layout = new VBox(
10,
new HBox(10,
chart,
new ImageView(chartImage)
),
exportLocation
);
layout.setAlignment(Pos.BASELINE_RIGHT);
layout.setPadding(new Insets(10));
Scene scene = new Scene(layout);
scene.getStylesheets().add(getClass().getResource(
"encoder-app.css"
).toExternalForm());
stage.setScene(scene);
stage.show();
logger.log(Level.INFO, "Wrote: " + imagePath);
}
private PieChart createChart() {
ObservableList<PieChart.Data> pieChartData =
FXCollections.observableArrayList(
new PieChart.Data("Grapefruit", 13),
new PieChart.Data("Oranges", 25),
new PieChart.Data("Plums", 10),
new PieChart.Data("Pears", 22),
new PieChart.Data("Apples", 30));
final PieChart chart = new PieChart(pieChartData);
chart.setTitle("Imported Fruits");
return chart;
}
private void exportPngSnapshot(
Node node,
Path path,
Paint backgroundFill
) throws IOException {
if (node.getScene() == null) {
Scene snapshotScene = new Scene(new Group(node));
}
SnapshotParameters params = new SnapshotParameters();
params.setFill(backgroundFill);
Image chartSnapshot = node.snapshot(params, null);
PngEncoderFX encoder = new PngEncoderFX(chartSnapshot, true);
byte[] bytes = encoder.pngEncode();
Files.write(path, bytes);
}
public static void main(String[] args) {
launch(args);
}
}
encoder-app.css - 测试工具的示例样式表
/** file: encoder-app.css **/
.root {
-fx-background-image: url(http://pixdaus.com/files/items/pics/7/92/275792_de0efe881e1a7e5da077a26eacfa5ed2_large.jpg);
-fx-background-size: cover;
}
.overlay-label {
-fx-background-color: rgba(0, 80, 0, 0.7);
-fx-text-fill: white;
}
chart.css - 测试工具的示例样式表
/** file: chart.css **/
.translucent-background {
-fx-background-color: rgba(127, 127, 60, 0.7);
}
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