かすみエッジは、100％の不透明度を取り戻す（処理）を保ちます

サボテン：

私は、次のコードを介して処理中にぼやけたエッジを持つ丸いブラシを作成しようとしています。実際のバージョンでは、私はから取らピクセルで描画しようとするため、円形形状を画素毎に描画されますPGraphic pg。

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();
            }
        }
    }
}

Rabbid76：

単一のドットを描く機能作成しPGraphicsたオブジェクトを：

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();
}

別々にドットを描画PGraphicsオブジェクトでsetup

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);
}

マウスをドラッグするときにブレンドpg_pen共通にPGraphicsオブジェクト（pg現在のマウス位置）。

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

完全性の追求のためのdraw機能：

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

---

[...]と黒の部分の上に描画する白い部分から色を取得しようとしました。

Add a color parameter to the DrawPen function and clear the pen PGraphics before drawing to it:

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();
}

Get the color in the mouse pressed event call back and change the color of the pen:

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

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

Note, the color is get from the pg object and not from the screen. If you want to get the color from the screen then it has to be (without .pg):

color c = get(mouseX, mouseY);

Further the color is changed any time when any mouse is pressed (pressed not dragged). Possibly you want to change the color when the right mouse button is pressed and paint when the left mouse button is pressed:

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