理论上,这应该是一个倾听
captureEvent()
获取新帧并跟踪第一帧之前是否已录制,如果已录制,则跟踪之后的第二帧。
下面是一个基本的注释草图来说明这一点(按任意键获取另一对帧):
import processing.video.*;
Capture camera;
PImage firstFrame;
PImage secondFrame;
void setup(){
size(1920,480);
camera = new Capture(this,640,480);
camera.start();
}
void draw(){
image(camera,0,0);
if(firstFrame != null){
image(firstFrame,640,0);
}
if(secondFrame != null){
image(secondFrame,1280,0);
}
}
//this is the callback from the video library when a new camera frame is available
void captureEvent(Capture c){
//read a new frame
c.read();
//if the first frame wasn't recorded yet, record(copy) it's pixels
if(firstFrame == null){
firstFrame = c.get();
}
//same for the second frame, but check if the first frame has been recorded first
if(firstFrame != null && secondFrame == null){
secondFrame = c.get();
}
}
void keyPressed(){
//reset consecutive frames on keypress
firstFrame = secondFrame = null;
}
理论上(正如您在
Processing Video Library's source code
),captureEvent仅在新相机样本准备就绪时激发。
在实践中,您会发现两个连续的帧可能看起来完全相同(即使它们在时间上可能是一分为二的),甚至是您在评论中指出的噪音。
感觉你所追求的是一个连续的帧,但与之前的帧有很大的不同。如果是这样的话,你可以和
FrameDifferencing example
(
处理(>);示例(>);库(>);视频(>);捕获(>);帧差分
)
这是上述草图的一个修改版本,使用戈兰·莱文的帧差分代码仅获取第二帧(如果相差一点点):
import processing.video.*;
Capture camera;
PImage firstFrame;
PImage secondFrame;
PImage diff;
void setup(){
size(1920,960);
camera = new Capture(this,640,480);
camera.start();
diff = createImage(640,480,RGB);
}
void draw(){
image(camera,0,0);
if(firstFrame != null){
image(firstFrame,640,0);
}
if(secondFrame != null){
image(secondFrame,1280,0);
}
image(diff,0,480);
}
//this is the callback from the video library when a new camera frame is available
void captureEvent(Capture c){
//read a new frame
c.read();
//if the first frame wasn't recorded yet, record(copy) it's pixels
if(firstFrame == null){
firstFrame = c.get();
println("recorded first frame at",new java.util.Date());
}
//same for the second frame, but check if the first frame has been recorded first
if(firstFrame != null && secondFrame == null){
//if the difference between the first frame cand the current frame is even ever so slightly off, record the second frame
if(difference(firstFrame,camera) > 100){
secondFrame = c.get();
}
}
}
int difference(PImage first,PImage second){
final int numPixels = 640*480;
camera.loadPixels();
int movementSum = 0; // Amount of movement in the frame
for (int i = 0; i < numPixels; i++) { // For each pixel in the video frame...
color currColor = first.pixels[i];
color prevColor = second.pixels[i];
// Extract the red, green, and blue components from current pixel
int currR = (currColor >> 16) & 0xFF; // Like red(), but faster
int currG = (currColor >> 8) & 0xFF;
int currB = currColor & 0xFF;
// Extract red, green, and blue components from previous pixel
int prevR = (prevColor >> 16) & 0xFF;
int prevG = (prevColor >> 8) & 0xFF;
int prevB = prevColor & 0xFF;
// Compute the difference of the red, green, and blue values
int diffR = abs(currR - prevR);
int diffG = abs(currG - prevG);
int diffB = abs(currB - prevB);
// Render the difference image to the screen
diff.pixels[i] = color(diffR, diffG, diffB);
// Add these differences to the running tally
movementSum += diffR + diffG + diffB;
}
diff.updatePixels();
return movementSum;
}
void keyPressed(){
//reset consecutive frames on keypress
firstFrame = secondFrame = null;
}
在这个例子中,100是一个任意值。
最大值为
255*3*640*480
(每个通道0-255个*通道数*宽度*高度)
