java - 在java中将图像的像素复制到 Canvas

Question

编辑:我更改了一些代码以反射(reflect) AlamasB 所说的内容。我仍然不明白应该如何填充字节数组以及需要进行哪些转换。

我正在尝试操作用户上传的图像的像素并将新图像写入 Canvas 上。现在我只是尝试复制原始图像而不更改像素的 RGB。我已经被困在同一个地方很长一段时间了，不知道下一步该去哪里。在代码的第一部分中，我复制了用户上传的原始图像。

   Image image = imageView.getImage();
   PixelReader pixelReader = image.getPixelReader();
   PixelFormat format = pixelReader.getPixelFormat();

   int width= (int)image.getWidth();
   int height = (int) image.getHeight();

   GraphicsContext gc = canvas.getGraphicsContext2D();
   PixelWriter pw = gc.getPixelWriter();

   byte[] imageData = new byte[width * height * 4];
   imageData = createImageData(imageData, pixelReader, width, height); 

    //..        
    //...the next function populates my byte array with what's in the image 

  public byte[] createImageData(byte[] imageData, PixelReader pr, int width, int height){
    int i = 0;
    for(int y=0; y<height; y++){
        for(int x = 0; x < width; x++){
            int argb = pixelReader.getArgb(x, y);
            imageData[i] = (byte) argb;
            imageData[i+1] = (byte) argb;
            imageData[i+2] = (byte) argb;
            i+=3;
            pw.setArgb(x, y, argb);
        }
    }


    return imageData;
}

编辑:不再使用此功能。下一个功能真的让我很困惑。我指的是这个http://docs.oracle.com/javafx/2/image_ops/jfxpub-image_ops.htm作为引用，但我不知道发生了什么。

//...  
//... the next function sets the pixels of the canvas to what's in the byte array

public void drawImageData(byte[] imageData, PixelWriter pw, int width, int height){
    boolean on = true;
    PixelFormat<ByteBuffer> pixelFormat = PixelFormat.getByteRgbInstance();
    for(int y = 50; y < 150; y+=height){
        for(int x = 50; x < 150; x+=width){
            if(on){
                pw.setPixels(x, y, width, height, pixelFormat, imageData, 0, width*3);
            }
            on = !on;
        }
        on=!on;
    }
}

Answer 1

考虑到 PixelReader 提供 getARGB在这种情况下，最好的选择可能是使用 32 位表示。随后将其转换为 4 字节数组，即 width * height * 4。最后使用setARGB绘制图像。

int argb = pixelReader.getArgb(x, y);
// populate imageData[i,i+1,i+2,i+3] by converting argb
...
// convert imageData[i,i+1,i+2,i+3] into a 32bit argb, say int argb2
pixelWriter.setArgb(x, y, argb2);

或者，您可以使用 Color 的 getOpacity() 从 RGBA 获取 A。再次使用 32 位表示。

至少这将为您提供一个最小的工作示例，然后您可以扩展它。

这是一个快速版本(独立，只需复制和粘贴):

import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.image.*;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

import java.nio.ByteBuffer;
import java.util.Arrays;

public class ImageManipulationApp extends Application {

    private static final int APP_W = 800;
    private static final int APP_H = 600;

    private Parent createContent() {
        Image image = makeMockImage();
        byte[] imageData = imageToData(image);

        byte[] modifiedImageData = modify(imageData);
        Image modifiedImage = dataToImage(modifiedImageData);

        HBox root = new HBox(25);
        root.getChildren().addAll(new ImageView(image), new ImageView(modifiedImage));

        return root;
    }

    private Image makeMockImage() {
        WritableImage image = new WritableImage(APP_W / 2, APP_H);
        PixelWriter writer = image.getPixelWriter();

        for (int y = 0; y < APP_H; y++) {
            for (int x = 0; x < APP_W / 2; x++) {
                writer.setColor(x, y, Math.random() < 0.00005 ? Color.YELLOW : Color.BLACK);
            }
        }

        return image;
    }

    /**
     * Modifies the pixel data.
     *
     * @param data original image data
     * @return modified image data
     */
    private byte[] modify(byte[] data) {
        // this is where changes happen
        return data;
    }

    private byte[] imageToData(Image image) {
        int width = (int) image.getWidth();
        int height = (int) image.getHeight();

        byte[] data = new byte[width * height * 4];

        int i = 0;

        for (int y = 0; y < height; y++){
            for (int x = 0; x < width; x++){
                int argb = image.getPixelReader().getArgb(x, y);

                byte[] pixelData = ByteBuffer.allocate(4).putInt(argb).array();

                data[i++] = pixelData[0];
                data[i++] = pixelData[1];
                data[i++] = pixelData[2];
                data[i++] = pixelData[3];
            }
        }

        return data;
    }

    private Image dataToImage(byte[] data) {
        // if we don't know the image size beforehand we can encode width and height
        // into image data too
        WritableImage image = new WritableImage(APP_W / 2, APP_H);
        PixelWriter writer = image.getPixelWriter();

        int i = 0;
        for (int y = 0; y < APP_H; y++) {
            for (int x = 0; x < APP_W / 2; x++) {
                int argb = ByteBuffer.wrap(Arrays.copyOfRange(data, i, i + 4)).getInt();

                writer.setArgb(x, y, argb);

                i += 4;
            }
        }

        return image;
    }

    @Override
    public void start(Stage stage) throws Exception {
        stage.setScene(new Scene(createContent()));
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}