java小林·吴氏算法

Question

我试图编写吴小林的算法，但我被卡住了。

似乎它应该可以工作，但不是，线条是完全光栅化的巫师完全不透明，有人知道为什么吗？非常感谢。我将其与pseoudo代码进行了比较，它看起来非常相似。我认为在选择颜色时会出现错误。

代码：

public class LineRasterizerXiaolinWu {

private RasterImage img;
private int color;
double gradient;

public LineRasterizerXiaolinWu(RasterImage img) {
    this.img = img;
}

public RasterImage rasterizeLine(int x1, int y1,
                                 int x2, int y2) {

    RasterImage result = img;

    boolean steep = Math.abs(y2-y1)> Math.abs(x2-x1);

    if(steep){
        int c = y1;
        y1 = x1;
        x1 = c;
        c = x2;
        x2 = y2;
        y2 = c;
    }
    if(x2 < x1) {
        int d = x2;
        x2 = x1;
        x1 = d;
        d = y2;
        y2 = y1;
        y1 = d;
    }

    double dx = x2 - x1;
    double dy = y2 - y1;

    if (dx == 0.0){
        gradient =1;
    }else {
        gradient = dy / dx;
    }

    //first end point
    int xEnd = round(x1);
    int yEnd = (int)(y1+gradient*(xEnd-x1));
    int xGap = (int) rfpart(x1+0.5);

    int xPxl1 = xEnd;
    int yPxl1 = (int)ipart(yEnd);

    if (steep) {
        plot(yPxl1, xPxl1, rfpart(yEnd)*xGap);
        plot((yPxl1 + 1), xPxl1, fpart(yEnd)*xGap);
    } else {
        plot(xPxl1, yPxl1, rfpart(yEnd) * xGap);
        plot(xPxl1, yPxl1 + 1, fpart(yEnd) * xGap);
    }

    double intery = yEnd + gradient;

    //second end point
    xEnd = round(x2);
    yEnd = (int)(y2+gradient*(xEnd-x2));
    xGap = (int) rfpart(x2+0.5);

    int xPxl2 = xEnd;
    int yPxl2 = (int)ipart(yEnd);

    if (steep) {
        plot(yPxl2, xPxl2, rfpart(yEnd)*xGap);
        plot((yPxl2 + 1), xPxl2, fpart(yEnd)*xGap);
    } else {
        plot(xPxl2, yPxl2, rfpart(yEnd) * xGap);
        plot(xPxl2, yPxl2 + 1, fpart(yEnd) * xGap);
    }

    if(steep){
        for(int i = xPxl1+1; i<=xPxl2-1; i++){
            plot((int)ipart(intery),i,rfpart(intery));
            plot((int)ipart(intery)+1,i,fpart(intery));
            intery +=gradient;
        }
    }else {
        for(int i = xPxl1+1; i<=xPxl2-1; i++){
            plot(i,(int)ipart(intery),rfpart(intery));
            plot(i,(int)ipart(intery)+1,fpart(intery));
            intery +=gradient;
        }
    }
    return result;
}

private void plot(int x, int y, double intensity){
    double alfaChanel = Math.round(intensity*100.0)/100.0;

    if (alfaChanel >= 0 && alfaChanel <= 0.2) {
        color =  (new Color(1.0f, 0.0f, 0.0f, 1.0f)).getRGB();
    } else if (alfaChanel > 0.2 && alfaChanel <= 0.4) {
        color =  (new Color(1.0f, 0.0f, 0.0f, 0.8f)).getRGB();
    } else if (alfaChanel > 0.4 && alfaChanel <= 0.6) {
        color =  (new Color(1.0f, 0.0f, 0.0f, 0.6f)).getRGB();
    } else if (alfaChanel > 0.6 && alfaChanel <= 0.8) {
        color =  (new Color(1.0f, 0.0f, 0.0f, 0.4f)).getRGB();
    } else if (alfaChanel > 0.8 && alfaChanel <= 1.0) {
        color =  (new Color(1.0f, 0.0f, 0.0f, 0.2f)).getRGB();
    }



    img.withPixel(x,y,color);
}

//integer part of x
private double ipart (double x){
    return Math.floor(x);
}

private int round (double x){
    return (int) Math.round(x+0.5);
}

//fractional part of x
private double fpart (double x){
    return x-Math.floor(x);
}

private double rfpart (double x){
    return 1-fpart(x);
}

结果：

​

​

Answer 1

通过添加以下方法解决了问题：

 private int blend (int a, int b, float ratio) {
    if (ratio > 1f) {
        ratio = 1f;
    } else if (ratio < 0f) {
        ratio = 0f;
    }

    float iRatio = 1.0f - ratio;

    int aA = (a >> 24 & 0xff);
    int aR = ((a & 0xff0000) >> 16);
    int aG = ((a & 0xff00) >> 8);
    int aB = (a & 0xff);

    int bA = (b >> 24 & 0xff);
    int bR = ((b & 0xff0000) >> 16);
    int bG = ((b & 0xff00) >> 8);
    int bB = (b & 0xff);

    int A = (int)((aA * iRatio) + (bA * ratio));
    int R = (int)((aR * iRatio) + (bR * ratio));
    int G = (int)((aG * iRatio) + (bG * ratio));
    int B = (int)((aB * iRatio) + (bB * ratio));

    return A << 24 | R << 16 | G << 8 | B;
}

并像这样选择颜色：

private void plot(int x, int y, double intensity){
    double alfaChanel = Math.round(intensity*100.0)/100.0;
    backGroundColor = 0xff2f2f2f;
    drawingColor = 0xffff0000;

    if (alfaChanel >= 0 && alfaChanel <= 0.2) {
        color = blend(backGroundColor,drawingColor,(float)alfaChanel);
    } else if (alfaChanel > 0.2 && alfaChanel <= 0.4) {
        color = blend(backGroundColor,drawingColor,(float)alfaChanel);
    } else if (alfaChanel > 0.4 && alfaChanel <= 0.6) {
        color = blend(backGroundColor,drawingColor,(float)alfaChanel);
    } else if (alfaChanel > 0.6 && alfaChanel <= 0.8) {
        color = blend(backGroundColor,drawingColor,(float)alfaChanel);
    } else if (alfaChanel > 0.8 && alfaChanel <= 1.0) {
        color = blend(backGroundColor,drawingColor,(float)alfaChanel);
    }

    img.withPixel(x,y,color);
}

谢谢