[英]How to show images in a large frequency in JavaFX?
我的應用程序生成熱圖圖像的速度與 CPU 一樣快(大約每秒 30-60 張),我想將它們顯示在一個“實時熱圖”中。 在 AWT/Swing 中,我可以將它們繪制成一個 JPanel,它就像一個魅力。 最近,我切換到JavaFX,並希望在這里實現相同的功能; 起初,我嘗試使用Canvas ,它很慢但還可以,但存在嚴重的內存泄漏問題,導致應用程序崩潰。 現在,我嘗試了ImageView組件 - 這顯然太慢了,因為圖像變得非常滯后(在每次新迭代中使用ImageView.setImage )。 據我了解,setImage 不保證在函數完成時實際顯示圖像。
我得到的印象是我走錯了路,以一種他們不適合的方式使用這些組件。 如何每秒顯示 30-60 張圖像?
編輯:一個非常簡單的測試應用程序。 您將需要JHeatChart庫。 請注意,在台式機上,我獲得了大約 70-80 FPS,並且可視化效果還不錯且流暢,但是在較小的樹莓派(我的目標機器)上,我獲得了大約 30 FPS,但是可視化效果非常卡。
package sample;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Scene;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import org.tc33.jheatchart.HeatChart;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.util.LinkedList;
public class Main extends Application {
ImageView imageView = new ImageView();
final int scale = 15;
@Override
public void start(Stage primaryStage) {
Thread generator = new Thread(() -> {
int col = 0;
LinkedList<Long> fps = new LinkedList<>();
while (true) {
fps.add(System.currentTimeMillis());
double[][] matrix = new double[48][128];
for (int i = 0; i < 48; i++) {
for (int j = 0; j < 128; j++) {
matrix[i][j] = col == j ? Math.random() : 0;
}
}
col = (col + 1) % 128;
HeatChart heatChart = new HeatChart(matrix, 0, 1);
heatChart.setShowXAxisValues(false);
heatChart.setShowYAxisValues(false);
heatChart.setLowValueColour(java.awt.Color.black);
heatChart.setHighValueColour(java.awt.Color.white);
heatChart.setAxisThickness(0);
heatChart.setChartMargin(0);
heatChart.setCellSize(new Dimension(1, 1));
long currentTime = System.currentTimeMillis();
fps.removeIf(elem -> currentTime - elem > 1000);
System.out.println(fps.size());
imageView.setImage(SwingFXUtils.toFXImage((BufferedImage) scale(heatChart.getChartImage(), scale), null));
}
});
VBox box = new VBox();
box.getChildren().add(imageView);
Scene scene = new Scene(box, 1920, 720);
primaryStage.setScene(scene);
primaryStage.show();
generator.start();
}
public static void main(String[] args) {
launch(args);
}
private static Image scale(Image image, int scale) {
BufferedImage res = new BufferedImage(image.getWidth(null) * scale, image.getHeight(null) * scale,
BufferedImage.TYPE_INT_ARGB);
AffineTransform at = new AffineTransform();
at.scale(scale, scale);
AffineTransformOp scaleOp =
new AffineTransformOp(at, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
return scaleOp.filter((BufferedImage) image, res);
}
}
您的代碼從后台線程更新 UI,這絕對是不允許的。 您需要確保從 FX 應用程序線程更新。 您還想嘗試“限制”實際的 UI 更新,使每個 JavaFX 幀渲染不超過一次。 最簡單的方法是使用AnimationTimer
,每次渲染一幀時都會調用其handle()
方法。
這是您執行此操作的代碼版本:
import java.awt.Dimension;
import java.awt.Image;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.util.LinkedList;
import java.util.concurrent.atomic.AtomicReference;
import org.tc33.jheatchart.HeatChart;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Scene;
import javafx.scene.image.ImageView;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class Main extends Application {
ImageView imageView = new ImageView();
final int scale = 15;
@Override
public void start(Stage primaryStage) {
AtomicReference<BufferedImage> image = new AtomicReference<>();
Thread generator = new Thread(() -> {
int col = 0;
LinkedList<Long> fps = new LinkedList<>();
while (true) {
fps.add(System.currentTimeMillis());
double[][] matrix = new double[48][128];
for (int i = 0; i < 48; i++) {
for (int j = 0; j < 128; j++) {
matrix[i][j] = col == j ? Math.random() : 0;
}
}
col = (col + 1) % 128;
HeatChart heatChart = new HeatChart(matrix, 0, 1);
heatChart.setShowXAxisValues(false);
heatChart.setShowYAxisValues(false);
heatChart.setLowValueColour(java.awt.Color.black);
heatChart.setHighValueColour(java.awt.Color.white);
heatChart.setAxisThickness(0);
heatChart.setChartMargin(0);
heatChart.setCellSize(new Dimension(1, 1));
long currentTime = System.currentTimeMillis();
fps.removeIf(elem -> currentTime - elem > 1000);
System.out.println(fps.size());
image.set((BufferedImage) scale(heatChart.getChartImage(), scale));
}
});
VBox box = new VBox();
box.getChildren().add(imageView);
Scene scene = new Scene(box, 1920, 720);
primaryStage.setScene(scene);
primaryStage.show();
generator.setDaemon(true);
generator.start();
AnimationTimer animation = new AnimationTimer() {
@Override
public void handle(long now) {
BufferedImage img = image.getAndSet(null);
if (img != null) {
imageView.setImage(SwingFXUtils.toFXImage(img, null));
}
}
};
animation.start();
}
public static void main(String[] args) {
launch(args);
}
private static Image scale(Image image, int scale) {
BufferedImage res = new BufferedImage(image.getWidth(null) * scale, image.getHeight(null) * scale,
BufferedImage.TYPE_INT_ARGB);
AffineTransform at = new AffineTransform();
at.scale(scale, scale);
AffineTransformOp scaleOp = new AffineTransformOp(at, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
return scaleOp.filter((BufferedImage) image, res);
}
}
使用AtomicReference
包裝緩沖圖像可確保它在兩個線程之間安全共享。
在我的機器上,這每秒生成大約 130 個圖像; 請注意,並非所有都顯示,因為每次 JavaFX 圖形框架顯示一幀(通常限制為 60fps)時,只會顯示最新的一個。
如果要確保顯示生成的所有圖像,即通過 JavaFX 幀率限制圖像生成,則可以使用BlockingQueue
來存儲圖像:
// AtomicReference<BufferedImage> image = new AtomicReference<>();
// Size of the queue is a trade-off between memory consumption
// and smoothness (essentially works as a buffer size)
BlockingQueue<BufferedImage> image = new ArrayBlockingQueue<>(5);
// ...
// image.set((BufferedImage) scale(heatChart.getChartImage(), scale));
try {
image.put((BufferedImage) scale(heatChart.getChartImage(), scale));
} catch (InterruptedException exc) {
Thread.currentThread.interrupt();
}
和
@Override
public void handle(long now) {
BufferedImage img = image.poll();
if (img != null) {
imageView.setImage(SwingFXUtils.toFXImage(img, null));
}
}
代碼效率很低,因為每次迭代都會生成一個新矩陣、新HeatChart
等。 這會導致在堆上創建許多對象並迅速丟棄,這會導致 GC 運行過於頻繁,尤其是在小內存機器上。 也就是說,我在最大堆大小設置為 64MB ( -Xmx64m
) 的情況下運行它,它仍然表現良好。 您或許可以優化代碼,但使用如上所示的AnimationTimer
,更快地生成圖像不會對 JavaFX 框架造成任何額外壓力。 我建議調查使用HeatChart
的可變性(即setZValues()
)以避免創建太多對象,和/或使用PixelBuffer
將數據直接寫入圖像視圖(這需要在 FX 應用程序線程上完成)。
這是一個不同的例子,它(幾乎)完全減少了對象的創建,使用一個屏幕外的int[]
數組來計算數據,並使用一個屏幕上的int[]
數組來顯示它。 有一些低級線程細節,以確保屏幕上的數組只能在一致的狀態下看到。 屏幕上的數組用於作為PixelBuffer
基礎,后者又用於WritableImage
。
這個類生成圖像數據:
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Consumer;
public class ImageGenerator {
private final int width;
private final int height;
// Keep two copies of the data: one which is not exposed
// that we modify on the fly during computation;
// another which we expose publicly.
// The publicly exposed one can be viewed only in a complete
// state if operations on it are synchronized on this object.
private final int[] privateData ;
private final int[] publicData ;
private final long[] frameTimes ;
private int currentFrameIndex ;
private final AtomicLong averageGenerationTime ;
private final ReentrantLock lock ;
private static final double TWO_PI = 2 * Math.PI;
private static final double PI_BY_TWELVE = Math.PI / 12; // 15 degrees
public ImageGenerator(int width, int height) {
super();
this.width = width;
this.height = height;
privateData = new int[width * height];
publicData = new int[width * height];
lock = new ReentrantLock();
this.frameTimes = new long[100];
this.averageGenerationTime = new AtomicLong();
}
public void generateImage(double angle) {
// compute in private data copy:
int minDim = Math.min(width, height);
int minR2 = minDim * minDim / 4;
for (int x = 0; x < width; x++) {
int xOff = x - width / 2;
int xOff2 = xOff * xOff;
for (int y = 0; y < height; y++) {
int index = x + y * width;
int yOff = y - height / 2;
int yOff2 = yOff * yOff;
int r2 = xOff2 + yOff2;
if (r2 > minR2) {
privateData[index] = 0xffffffff; // white
} else {
double theta = Math.atan2(yOff, xOff);
double delta = Math.abs(theta - angle);
if (delta > TWO_PI - PI_BY_TWELVE) {
delta = TWO_PI - delta;
}
if (delta < PI_BY_TWELVE) {
int green = (int) (255 * (1 - delta / PI_BY_TWELVE));
privateData[index] = (0xff << 24) | (green << 8); // green, fading away from center
} else {
privateData[index] = 0xff << 24; // black
}
}
}
}
// copy computed data to public data copy:
lock.lock();
try {
System.arraycopy(privateData, 0, publicData, 0, privateData.length);
} finally {
lock.unlock();
}
frameTimes[currentFrameIndex] = System.nanoTime() ;
int nextIndex = (currentFrameIndex + 1) % frameTimes.length ;
if (frameTimes[nextIndex] > 0) {
averageGenerationTime.set((frameTimes[currentFrameIndex] - frameTimes[nextIndex]) / frameTimes.length);
}
currentFrameIndex = nextIndex ;
}
public void consumeData(Consumer<int[]> consumer) {
lock.lock();
try {
consumer.accept(publicData);
} finally {
lock.unlock();
}
}
public long getAverageGenerationTime() {
return averageGenerationTime.get() ;
}
}
這是用戶界面:
import java.nio.IntBuffer;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelFormat;
import javafx.scene.image.PixelWriter;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class AnimationApp extends Application {
private final int size = 400 ;
private IntBuffer buffer ;
@Override
public void start(Stage primaryStage) throws Exception {
// background image data generation:
ImageGenerator generator = new ImageGenerator(size, size);
// Generate new image data as fast as possible:
Thread thread = new Thread(() -> {
while( true ) {
long now = System.currentTimeMillis() ;
double angle = 2 * Math.PI * (now % 10000) / 10000 - Math.PI;
generator.generateImage(angle);
}
});
thread.setDaemon(true);
thread.start();
generator.consumeData(data -> buffer = IntBuffer.wrap(data));
PixelFormat<IntBuffer> format = PixelFormat.getIntArgbPreInstance() ;
PixelBuffer<IntBuffer> pixelBuffer = new PixelBuffer<>(size, size, buffer, format);
WritableImage image = new WritableImage(pixelBuffer);
BorderPane root = new BorderPane(new ImageView(image));
Label fps = new Label("FPS: ");
root.setTop(fps);
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.setTitle("Give me a ping, Vasili. ");
primaryStage.show();
AnimationTimer animation = new AnimationTimer() {
@Override
public void handle(long now) {
// Update image, ensuring we only see the underlying
// data in a consistent state:
generator.consumeData(data -> {
pixelBuffer.updateBuffer(pb -> null);
});
long aveGenTime = generator.getAverageGenerationTime() ;
if (aveGenTime > 0) {
double aveFPS = 1.0 / (aveGenTime / 1_000_000_000.0);
fps.setText(String.format("FPS: %.2f", aveFPS));
}
}
};
animation.start();
}
public static void main(String[] args) {
Application.launch(args);
}
}
對於不依賴於 JavaFX 13 PixelBuffer
,您可以修改此類以使用PixelWriter
(AIUI 這不會那么有效,但在此示例中工作得同樣順利):
// generator.consumeData(data -> buffer = IntBuffer.wrap(data));
PixelFormat<IntBuffer> format = PixelFormat.getIntArgbPreInstance() ;
// PixelBuffer<IntBuffer> pixelBuffer = new PixelBuffer<>(size, size, buffer, format);
// WritableImage image = new WritableImage(pixelBuffer);
WritableImage image = new WritableImage(size, size);
PixelWriter pixelWriter = image.getPixelWriter() ;
和
AnimationTimer animation = new AnimationTimer() {
@Override
public void handle(long now) {
// Update image, ensuring we only see the underlying
// data in a consistent state:
generator.consumeData(data -> {
// pixelBuffer.updateBuffer(pb -> null);
pixelWriter.setPixels(0, 0, size, size, format, data, 0, size);
});
long aveGenTime = generator.getAverageGenerationTime() ;
if (aveGenTime > 0) {
double aveFPS = 1.0 / (aveGenTime / 1_000_000_000.0);
fps.setText(String.format("FPS: %.2f", aveFPS));
}
}
};
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