如何从外部if语句访问值[关闭]

Question

如何从

if

语句外部访问 var 值。我想从

brightestX

语句外部访问

if(video.available)

值。

void draw(){
  if (video.available()) 
  {
    video.read();
    image(video, 0, 0, width, height);
    int brightestX = 0; 
    int brightestY = 0; 
    float brightestValue = 0; 

    video.loadPixels();
    int index = 0;
   
    for ( int y = 0; y < video.height; y++) {
        for ( int x = 0; x < video.width; x++) {
          int pixelValue = video.pixels[index];
          float pixelBrightness = brightness(pixelValue);

          if (pixelBrightness > brightestValue) {
              brightestValue = pixelBrightness;        
              brightestY = y;
              brightestX = x;
          }
          index++;
        }
    }
    fill(255, 204, 0, 128);
    ellipse(brightestX, brightestY, 200, 200);  
  }
}

Answer 1

只需在

if

条件范围之外声明要访问的变量即可。您可以稍后在

if

条件中引用相同的变量来更新它们，然后在

if

之后您可以读取这些更新的值。当然，这些值只会在视频可播放时更新：

void draw(){
  int brightestX = 0; 
  int brightestY = 0; 
    
  if (video.available()) 
  {
    video.read();
    image(video, 0, 0, width, height);
    float brightestValue = 0; 

    video.loadPixels();
    int index = 0;

    for ( int y = 0; y < video.height; y++) {
        for ( int x = 0; x < video.width; x++) {
          int pixelValue = video.pixels[index];
          float pixelBrightness = brightness(pixelValue);

          if (pixelBrightness > brightestValue) {
              brightestValue = pixelBrightness;        
              brightestY = y;
              brightestX = x;
          }
          index++;
        }
    }
    fill(255, 204, 0, 128);
    ellipse(brightestX, brightestY, 200, 200);  
  }
  
  println(brightestX, brightestY); 
    
}

如果有帮助，另请查看 Java Scope。