Differences

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--- processing:video_capture [2013/04/12 18:48] – [Reduce resolution] mithat
+++ processing:video_capture [2013/08/15 22:40] – [Brightest pixel] mithat
@@ Line 1: / Line 1: @@
 ====== Video capture examples ======
-Examples below have been adapted from the [[http://www.processing.org/reference/libraries/video/Capture.html|Processing 2.0 library reference]] and from examples at [[http://www.learningprocessing.com/|Learning Processing]].
+The examples below are based on documentation and code from the [[http://www.processing.org/reference/libraries/video/Capture.html|Processing 2.0 library reference]] and at [[http://www.learningprocessing.com/|Learning Processing]].
 ===== List available capture devices =====
-The following sketch will print out a list of available capture devices to the console. You'll need at least one entry to do video capture. On Linux (the only platform I tested) different resolutions show up as different devices.
+You'll need at least one available device to do video capture. The following sketch will print out a list of available capture devices to the console. On Linux (the only platform I tested) different resolutions show up as different devices.
 <file java list_capture_devices.pde>
@@ Line 31: / Line 31: @@
 ===== Show video =====
+There are two ways you can set up video capture: by requesting capture parameters or specifying the device.
 ==== By requesting capture parameters ====
 <file java show_capture_by_parameters.pde>
@@ Line 66: / Line 68: @@
 ==== By specifying device ====
-Note that Processing will crop the capture to the canvas size if it doesn't fit.
+Processing will crop the capture to the canvas size if it doesn't fit.
 <file java show_capture_by_devnum.pde>
@@ Line 112: / Line 114: @@
 </file>
-<WRAP center round info 80%>
+<WRAP center round tip 80%>
 ===== Capture is a PImage =====
-Something the documentation on the ''Capture'' class doesn’t mention is that ''[[http://processing.org/reference/libraries/video/Capture.html|Capture]]'' is derived from ''[[http://processing.org/reference/PImage.html|PImage]]''. You need to dig into the ''Capture'' source code to figure that out:
+Something the [[http://processing.org/reference/libraries/video/Capture.html|documentation]] on the Capture class doesn’t mention is that Capture is derived from [[http://processing.org/reference/PImage.html|PImage]]. This is the key to manipulating Capture output. You need to dig into the Capture source code to figure that out:
 <code java>public class Capture extends PImage implements PConstants { ...</code>
-This means all the methods and fields available to ''PImage'' objects should also be available to ''Capture'' objects. This is the key to manipulating ''Capture'' output.
+This means all the methods and fields available to PImage objects should also be available to Capture objects.
 </WRAP>
@@ Line 262: / Line 265: @@
 </file>
+You can render grayscale instead of color above by replacing the line <code java>color c = img.pixels[col + row*img.width];</code> with <code java>float c = brightness(img.pixels[col + row*img.width]);</code>
+===== Brightest pixel =====
+The following example takes the reduced resolution camera feed above and draws a colored circle inside the brightest pixel found. If there is more than one pixel with the same brightness, then it shows the first one (scanning from top-left to bottom-right). It also adds some code to indicate frame timing.
+<file java capture_brightest_pixel.pde>
+/** Reduce resolution of captured image and indicate brightest pixel.
+ * @author Mithat Konar
+ */
+import processing.video.*;
+// === Program constants === //
+// Rendering parameters:
+// number of cells the rendered image should be in each direction:
+final int REDUCED_WIDTH = 32;
+final int REDUCED_HEIGHT = 24;
+// Canvas parameters:
+// number of times you want REDUCED image blown up:
+final int OUTPUT_SCALE = 20;
+// frame rate of rendered output:
+final int CANVAS_FPS = 6;  // should divide evenly into CAM_FPS
+// to avoid jitter.
+// Video capture parameters
+// (adjust as neeeded for your platform's available capture options):
+final int CAM_WIDTH = 320;
+final int CAM_HEIGHT = 240;
+final int CAM_FPS = 30;
+// === Global variables ===//
+Capture cam;  // The video capture device.
+PImage img;   // Buffer image.
+int blink_state = 0;
+// === GO! === //
+void setup() {
+  frameRate(CANVAS_FPS);
+  size(REDUCED_WIDTH*OUTPUT_SCALE, REDUCED_HEIGHT*OUTPUT_SCALE);
+  ellipseMode(CORNER);
+  if (Capture.list().length == 0) {
+    println("There are no cameras available for capture.");
+    exit();
+  }
+  // Instantiate a buffer image used for subsampling, etc.
+  img = createImage(REDUCED_WIDTH, REDUCED_HEIGHT, RGB);
+  // Instantiate a new Capture object, requesting the specs:
+  cam = new Capture(this, CAM_WIDTH, CAM_HEIGHT, CAM_FPS);
+  cam.start();  // In Processing 2.0, you need to start the capture device
+}
+void draw() {
+  int brightestCol = 0;
+  int brightestRow = 0;
+  float bightestIntensity = 0.0;
+  // Grab a frame
+  if (cam.available() == true) {
+    cam.read();
+  }
+  // We are using a buffer img because
+  // cam.resize(REDUCED_WIDTH, REDUCED_HEIGHT);
+  // doesn't work :-(
+  img.copy(cam, 0, 0, CAM_WIDTH, CAM_HEIGHT, 0, 0, REDUCED_WIDTH, REDUCED_HEIGHT);
+  img.loadPixels();
+  // For each column in img:
+  for (int col = 0; col < REDUCED_WIDTH; col++) {
+    // For each row in img:
+    for (int row = 0; row < REDUCED_HEIGHT; row++) {
+      // Draw the pixel intensity.
+      float pixelIntensity = brightness(img.pixels[col + row*img.width]);
+      fill(pixelIntensity);
+      stroke(pixelIntensity);
+      rect(col*OUTPUT_SCALE, row*OUTPUT_SCALE, OUTPUT_SCALE, OUTPUT_SCALE);
+      // Determine whether this is the brightest pixel in this frame.
+      if (pixelIntensity > bightestIntensity)
+      {
+        bightestIntensity = pixelIntensity;
+        brightestCol = col;
+        brightestRow = row;
+      }
+    }
+  }
+  // Highlight brightest pixel.
+  fill(#000000, 0);
+  stroke(#ff0000);
+  strokeWeight(2);
+  ellipse(brightestCol*OUTPUT_SCALE, brightestRow*OUTPUT_SCALE,
+       OUTPUT_SCALE, OUTPUT_SCALE);
+  // Frame timer
+  fill(#000099, 100);
+  stroke(#0000ff, 100);
+  strokeWeight(1);
+  blink_state = ++blink_state % CANVAS_FPS;
+  rect(0, 0, blink_state*OUTPUT_SCALE, OUTPUT_SCALE);
+}</file>