java - 模糊的边缘不断恢复 100% 的不透明度(处理中)

Question

我正在尝试通过以下代码在 Processing 中创建一个边缘模糊的圆形画笔。圆形是逐像素绘制的，因为在实际版本中，我尝试使用从 PGraphic pg 中获取的像素进行绘制。

PFont font;
PGraphics pg;
int X;
int Y;
int rad = 20;

void setup (){
    size(800, 800, P2D);
    background(0);
    noStroke();

    pg = createGraphics(800, 800, JAVA2D);
    pg.beginDraw();
    pg.fill(255);
    pg.noStroke();
    pg.textFont(font);
    pg.textSize(400);
    pg.pushMatrix();
    pg.translate(width/2, height/2-140);
    pg.textAlign(CENTER, CENTER);
    pg.text("b", 0 , 0);
    pg.popMatrix();
    pg.endDraw();
}

void draw () {
    image(pg,0,0);
}

void mousePressed(){
    X = mouseX;
    Y = mouseY;
}

void mouseDragged(){

    for (int x=0; x<rad; x++) {
        for (int y=0; y<rad; y++) {
        float distance = sqrt(pow(x,2)+pow(y,2));
        float alpha = 255-map(distance,0,rad,0,255);

            if (sqrt(pow(x,2)+pow(y,2)) < rad){
                pg.beginDraw();
                pg.set(mouseX+x,mouseY+y,color(255,255,255, alpha));
                pg.set(mouseX-x,mouseY+y,color(255,255,255, alpha));
                pg.set(mouseX+x,mouseY-y,color(255,255,255, alpha));
                pg.set(mouseX-x,mouseY-y,color(255,255,255, alpha));
                pg.endDraw();
            }
        }
    }
}

Answer 1

创建一个将单个点绘制到 PGraphics 对象的函数:

void DrawPen(PGraphics pg, int cptX, int cptY, int r) {
    pg.beginDraw();
    for (int x = 0; x < r; ++x) {
        for (int y = 0; y < r; ++y) {
          float distance = sqrt(x*x + y*y);
          float alpha = 255-map(distance,0,r,0,255);
          if (distance < r) {
              pg.set(cptX+x,cptY+y,color(255,255,255, alpha));
              pg.set(cptX-x,cptY+y,color(255,255,255, alpha));
              pg.set(cptX+x,cptY-y,color(255,255,255, alpha));
              pg.set(cptX-x,cptY-y,color(255,255,255, alpha));
          }
        }
    }
    pg.endDraw();
}

在 setup 中为单独的 PGraphics 对象画一个点

PGraphics pg;
PGraphics pg_pen;
int rad = 20;

void setup (){
    size(800, 800, P2D);

    pg = createGraphics(800, 800, JAVA2D);
    pg.beginDraw();
    // [...]
    pg.endDraw();

    pg_pen = createGraphics(2*rad, 2*rad, JAVA2D);
    DrawPen(pg_pen, rad, rad, rad);
}

当拖动鼠标时，将 pg_pen 混合到当前鼠标位置的普通 PGraphics 对象 (pg):

void mouseDragged(){
    pg.beginDraw();
    pg.image(pg_pen, mouseX-rad, mouseY-rad);
    pg.endDraw();
}

为了寻求完整性，draw 函数:

void draw () {
    background(0); 
    image(pg,0,0);
}

---

[...] and tried to get the color from the white part to draw on the black part.

向 DrawPen 函数添加一个 color 参数并在绘制之前清除笔 PGraphics:

void DrawPen(PGraphics pg, int cptX, int cptY, int r, color c) {
    pg.beginDraw();
    pg.clear();
    for (int x = 0; x < r; ++x) {
        for (int y = 0; y < r; ++y) {
          float distance = sqrt(x*x + y*y);
          float alpha = 255-map(distance,0,r,0,255);
          if (distance < r) {
              color pc = color(red(c),green(c),blue(c), alpha);
              pg.set(cptX+x,cptY+y,pc);
              pg.set(cptX-x,cptY+y,pc);
              pg.set(cptX+x,cptY-y,pc);
              pg.set(cptX-x,cptY-y,pc);
          }
        }
    }
    pg.endDraw();
}

在鼠标按下事件回调中获取颜色并改变笔的颜色:

void mousePressed() {
    color c = pg.get(mouseX, mouseY);
    println(c);

    DrawPen(pg_pen, rad, rad, rad, c);
}

请注意，颜色是从 pg 对象中获取的，而不是从屏幕中获取的。如果你想从屏幕上获取颜色，那么它必须是(没有 .pg):

color c = get(mouseX, mouseY);

此外，只要按下任何鼠标(按下而不是拖动)，颜色就会随时更改。可能您想在按下鼠标右键时更改颜色并在按下鼠标左键时绘制:

void mousePressed() {
    if (mouseButton == RIGHT) {
        color c = pg.get(mouseX, mouseY);
        println(c);
        DrawPen(pg_pen, rad, rad, rad, c);
    }
}