image-processing - 处理草图不会在屏幕上显示修改后的图像

Question

我正在制作一个草图，它执行以下操作：

调整大图像的大小以适应800 x 600屏幕。

显示图像

按下按键时应用一些效果

在屏幕上显示图像并打印一条小Done消息

一切正常，期望它不能正确显示图像。

这是黑白效果：

void blackAndWhite() {
  loadPixels();
  for (int i = 0;i < img.pixels.length;i++) {
    int pixel = img.pixels[i];

    // println("Working on pixel " + i + " out of " + img.pixels.length); 

    int red = (int) red(pixel);
    int green = (int) green(pixel);
    int blue = (int) blue(pixel);

    /*
     * Luminosity Method.
     */
    //      red = (int) (red * 0.21);
    //      green = (int) (green * 0.71);
    //      blue = (int) (blue * 0.07);

    /*
     * Average Method
     */
    //  float avg = (int) (red + green + blue / 3);
    //  red = green = blue = (int) avg;

    /*
     * Lightness Method
     */
    int mostProminent = max(red, green, blue);
    int leastProminent = min(red, green, blue);
    int avg = (int) ((mostProminent + leastProminent) / 2);
    red = green = blue = avg;

    pixel = color(red, green, blue);
    img.pixels[i] = pixel;
  }
  println("Done");
  updatePixels();
  image(img, WIDTH/2, HEIGHT/2, calculatedWidth, calculatedHeight);
}  

但是，只显示彩色图像:(
我知道该算法有效，因为我已经在其他图像上尝试过它（不使用这个草图）。
出了什么问题？

Answer 1

以下代码工作正常：

PImage img;

void setup () {
  img = loadImage ("img.png");
  size(img.width, img.height);
}

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

void keyReleased () {
  blackAndWhite();
}

void blackAndWhite() {

  img.loadPixels();
  for (int i = 0;i < img.pixels.length;i++) {
    int pixel = img.pixels[i];

    // println("Working on pixel " + i + " out of " + img.pixels.length); 

    int red = (int) red(pixel);
    int green = (int) green(pixel);
    int blue = (int) blue(pixel);

    /*
     * Luminosity Method.
     */
    //      red = (int) (red * 0.21);
    //      green = (int) (green * 0.71);
    //      blue = (int) (blue * 0.07);

    /*
     * Average Method
     */
    //  float avg = (int) (red + green + blue / 3);
    //  red = green = blue = (int) avg;

    /*
     * Lightness Method
     */
    int mostProminent = max(red, green, blue);
    int leastProminent = min(red, green, blue);
    int avg = (int) ((mostProminent + leastProminent) / 2);
    red = green = blue = avg;

    pixel = color(red, green, blue);
    img.pixels[i] = pixel;
  }
  println("Done");
  img.updatePixels();
} 

我的猜测是你要么忘记写img .loadPixels() 而不是 loadPixels()，要么是草图的draw()方法有问题。