如何验证目标像素是否在某个屏幕范围内

如何解决如何验证目标像素是否在某个屏幕范围内

如何检查屏幕特定区域内是否有目标像素，例如验证是否有 x 320 的目标像素。 x 和 y 是屏幕的宽度和高度。

在下面的代码中，我能够跟踪目标像素的平均 x,y。 此代码正在使用处理草图和着色器程序（glsl） 感谢您的帮助

    import processing.video.*;
    PShader colorFinder,colorPosShader;
    PGraphics overlay,posBuffer;
    // Variable for capture device
    Capture video;
    
    // A variable for the color we are searching for.
    color trackColor; 
    float threshold = 0.1;
    
    void setup() {
      //size(320,240);
      size(640,480,P2D);
      overlay = createGraphics(width,height,P2D);
      posBuffer = createGraphics(width,P2D);
      colorFinder = loadShader("colorDetect.glsl");
      colorPosShader = loadShader("colorPos.glsl");
      printArray(Capture.list());
      video = new Capture(this,width,height);
      video.start();
      video.loadPixels();
      // Start off tracking for red
      trackColor = color(255,0);
    }
    
    void captureEvent(Capture video) {
      // Read image from the camera
      video.read();
    }
    
    void draw() {
      colorFinder.set("threshold",threshold);
      colorFinder.set("targetColor",red(trackColor) / 255.0,green(trackColor) / 255.0,blue(trackColor) / 255.0,1.0);
      colorPosShader.set("threshold",threshold);
      colorPosShader.set("targetColor",1.0);
      overlay.beginDraw();
      overlay.shader(colorFinder);
      overlay.image(video,0);
      overlay.endDraw();
      posBuffer.beginDraw();
      posBuffer.shader(colorPosShader);
      posBuffer.image(video,0);
      posBuffer.endDraw();
      //compute average position by looking at pixels from position buffer
      posBuffer.loadPixels();
      PVector avg = new PVector(0,0);
      int count = 0;
      for(int i = 0; i < posBuffer.pixels.length; i++){
        // encoded so blue is > 0 if a pixel is within threshold
        if(blue(posBuffer.pixels[i]) > 0){
          count++;
          // processing takes 0-1 (float) color values from shader to 0-255 (int) values for color
          // to decode,we need to divide the color by 255 to get the original value
          avg.add(red(posBuffer.pixels[i]) / 255.0,green(posBuffer.pixels[i]) / 255.0);
        }
      }
      if(count > 0){
        // we have the sum of positions,so divide by the number of additions
        avg.div((float) count);
        // convert 0-1 position to screen position
        avg.x *= width;
        avg.y *= height;
      } else {
        // appear offscreen
        avg = new PVector(-100,-100);
      }
      image(overlay,0);
      fill(trackColor);
      stroke(0);
      circle(avg.x,avg.y,16);
      fill(0,50);
      nostroke();
      rect(0,150,30);
      fill(150);
      //text("avg,x" + avg.x,11);
      //text("Threshold: " + threshold,22);
      println(frameRate);
      println(count);
    }
    
    void mousepressed() {
      // Save color where the mouse is clicked in trackColor variable
      video.loadPixels();
      int loc = mouseX + mouseY*video.width;
      trackColor = video.pixels[loc];
    }
    
    void mouseWheel(MouseEvent e){
      threshold -= e.getCount() * 0.01;
      threshold = constrain(threshold,1);
    }
    


        // this shader for detect color
    //the shader to find pixels if they are within a threshold:
    In shaders,colors are stored with 4 component vectors with 
    //each component ranging from 0 to 1. The components are usually marked x,y,z,and w
    #ifdef GL_ES
    precision mediump float;
    precision mediump int;
    #endif
    
    uniform sampler2D texture;
    
    varying vec4 vertColor;
    varying vec4 vertTexCoord;
    //Uniform variables are constants in the shader,but can be modified by the external 
    //program that calls the shader,in this case the processing sketch
    uniform vec4 targetColor;
    uniform float threshold; //between 0 and 1
    
    void main() {
    // get pixel color
    vec4 texColor = texture2D(texture,vertTexCoord.st) * vertColor;
    vec3 a = texColor.xyz;
    vec3 b = targetColor.xyz;
    // compute "distance" between colors rgb components
    float dist = sqrt((b.x - a.x) * (b.x - a.x) + (b.y - a.y) * (b.y - a.y) + (b.z - a.z) * (b.z - a.z));
    // colors are from 0-1,so the max distance between colors is sqrt(3)
    if(dist < threshold * sqrt(3)){
    // display inverse color where pixels are within the threshold
    texColor = vec4(1) - texColor;
    }
    // force alpha to be 1 since inverting the color makes the alpha zero
    gl_FragColor = vec4(texColor.xyz,1);
    }


    //this shader finding the positions of all detected pixels
#ifdef GL_ES
precision mediump float;
precision mediump int;
#endif

uniform sampler2D texture;

varying vec4 vertColor;
varying vec4 vertTexCoord;//uv coordinates of the texture
    //or uv coordinate of the current pixel on the screen
    //uv coordinates are a 2D vector that ranges from 0-1 in each 
    //component,where a uv of (0,0) means you are at 
    //the top-left corner of the texture and (1,1) the bottom right
//To get the screen position,you multiply the uv by the screen width and height
uniform vec4 targetColor;
uniform float threshold; //between 0 and 1


void main() {
vec4 texColor = texture2D(texture,vertTexCoord.st) * vertColor;
vec3 a = texColor.xyz;
vec3 b = targetColor.xyz;
float dist = sqrt((b.x - a.x) * (b.x - a.x) + (b.y - a.y) * (b.y - a.y) + (b.z - a.z) * (b.z - a.z));
bool cond = dist < threshold * sqrt(3);
// if color is within threshold,encode the pixel's position into red and green components
// and use blue component as a marker that the pixel was in range
// vertTexCoord is from 0 to 1,so after computing average,multiply by width and height to get screen position
gl_FragColor = cond ? vec4(vertTexCoord.x,vertTexCoord.y,1,1) : vec4(0,1);
}