我从这个链接中获取的代码：
http://www.stanford.edu/class/ee368/Android/index.html
项目：颜色直方图 它在我的设备上实时显示直方图。
问题在于，如果我正常使用我的设备相机，它会快速平稳地移动，我的意思是我在不录制视频或拍照的情况下移动我的设备，而且移动速度非常快。
但是一旦我使用这个项目并实时显示直方图，它就会慢得多。
问题是为什么？如果有任何方法可以使它更顺畅和更快？
这是主要代码：
package com.example.viewfinderee368;
import java.io.IOException;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;
import android.view.WindowManager;
// ----------------------------------------------------------------------
public class ViewfinderEE368 extends Activity {
private Preview mPreview;
private DrawOnTop mDrawOnTop;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Hide the window title.
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
requestWindowFeature(Window.FEATURE_NO_TITLE);
// Create our Preview view and set it as the content of our activity.
// Create our DrawOnTop view.
mDrawOnTop = new DrawOnTop(this);
mPreview = new Preview(this, mDrawOnTop);
setContentView(mPreview);
addContentView(mDrawOnTop, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
}
}
//----------------------------------------------------------------------
class DrawOnTop extends View {
Bitmap mBitmap;
Paint mPaintBlack;
Paint mPaintYellow;
Paint mPaintRed;
Paint mPaintGreen;
Paint mPaintBlue;
byte[] mYUVData;
int[] mRGBData;
int mImageWidth, mImageHeight;
int[] mRedHistogram;
int[] mGreenHistogram;
int[] mBlueHistogram;
double[] mBinSquared;
public DrawOnTop(Context context) {
super(context);
mPaintBlack = new Paint();
mPaintBlack.setStyle(Paint.Style.FILL);
mPaintBlack.setColor(Color.BLACK);
mPaintBlack.setTextSize(25);
mPaintYellow = new Paint();
mPaintYellow.setStyle(Paint.Style.FILL);
mPaintYellow.setColor(Color.YELLOW);
mPaintYellow.setTextSize(25);
mPaintRed = new Paint();
mPaintRed.setStyle(Paint.Style.FILL);
mPaintRed.setColor(Color.RED);
mPaintRed.setTextSize(25);
mPaintGreen = new Paint();
mPaintGreen.setStyle(Paint.Style.FILL);
mPaintGreen.setColor(Color.GREEN);
mPaintGreen.setTextSize(25);
mPaintBlue = new Paint();
mPaintBlue.setStyle(Paint.Style.FILL);
mPaintBlue.setColor(Color.BLUE);
mPaintBlue.setTextSize(25);
mBitmap = null;
mYUVData = null;
mRGBData = null;
mRedHistogram = new int[256];
mGreenHistogram = new int[256];
mBlueHistogram = new int[256];
mBinSquared = new double[256];
for (int bin = 0; bin < 256; bin++)
{
mBinSquared[bin] = ((double)bin) * bin;
} // bin
}
@Override
protected void onDraw(Canvas canvas) {
if (mBitmap != null)
{
int canvasWidth = canvas.getWidth();
int canvasHeight = canvas.getHeight();
int newImageWidth = canvasWidth;
int newImageHeight = canvasHeight;
int marginWidth = (canvasWidth - newImageWidth)/2;
// Convert from YUV to RGB
decodeYUV420SP(mRGBData, mYUVData, mImageWidth, mImageHeight);
// Draw bitmap
mBitmap.setPixels(mRGBData, 0, mImageWidth, 0, 0,
mImageWidth, mImageHeight);
Rect src = new Rect(0, 0, mImageWidth, mImageHeight);
Rect dst = new Rect(marginWidth, 0,
canvasWidth-marginWidth, canvasHeight);
canvas.drawBitmap(mBitmap, src, dst, mPaintBlack);
// Draw black borders
canvas.drawRect(0, 0, marginWidth, canvasHeight, mPaintBlack);
canvas.drawRect(canvasWidth - marginWidth, 0,
canvasWidth, canvasHeight, mPaintBlack);
// Calculate histogram
calculateIntensityHistogram(mRGBData, mRedHistogram,
mImageWidth, mImageHeight, 0);
calculateIntensityHistogram(mRGBData, mGreenHistogram,
mImageWidth, mImageHeight, 1);
calculateIntensityHistogram(mRGBData, mBlueHistogram,
mImageWidth, mImageHeight, 2);
// Calculate mean
double imageRedMean = 0, imageGreenMean = 0, imageBlueMean = 0;
double redHistogramSum = 0, greenHistogramSum = 0, blueHistogramSum = 0;
for (int bin = 0; bin < 256; bin++)
{
imageRedMean += mRedHistogram[bin] * bin;
redHistogramSum += mRedHistogram[bin];
imageGreenMean += mGreenHistogram[bin] * bin;
greenHistogramSum += mGreenHistogram[bin];
imageBlueMean += mBlueHistogram[bin] * bin;
blueHistogramSum += mBlueHistogram[bin];
} // bin
imageRedMean /= redHistogramSum;
imageGreenMean /= greenHistogramSum;
imageBlueMean /= blueHistogramSum;
// Calculate second moment
double imageRed2ndMoment = 0, imageGreen2ndMoment = 0, imageBlue2ndMoment = 0;
for (int bin = 0; bin < 256; bin++)
{
imageRed2ndMoment += mRedHistogram[bin] * mBinSquared[bin];
imageGreen2ndMoment += mGreenHistogram[bin] * mBinSquared[bin];
imageBlue2ndMoment += mBlueHistogram[bin] * mBinSquared[bin];
} // bin
imageRed2ndMoment /= redHistogramSum;
imageGreen2ndMoment /= greenHistogramSum;
imageBlue2ndMoment /= blueHistogramSum;
double imageRedStdDev = Math.sqrt( imageRed2ndMoment - imageRedMean*imageRedMean );
double imageGreenStdDev = Math.sqrt( imageGreen2ndMoment - imageGreenMean*imageGreenMean );
double imageBlueStdDev = Math.sqrt( imageBlue2ndMoment - imageBlueMean*imageBlueMean );
// Draw mean
String imageMeanStr = "Mean (R,G,B): " + String.format("%.4g", imageRedMean) + ", " + String.format("%.4g", imageGreenMean) + ", " + String.format("%.4g", imageBlueMean);
canvas.drawText(imageMeanStr, marginWidth+10-1, 30-1, mPaintBlack);
canvas.drawText(imageMeanStr, marginWidth+10+1, 30-1, mPaintBlack);
canvas.drawText(imageMeanStr, marginWidth+10+1, 30+1, mPaintBlack);
canvas.drawText(imageMeanStr, marginWidth+10-1, 30+1, mPaintBlack);
canvas.drawText(imageMeanStr, marginWidth+10, 30, mPaintYellow);
// Draw standard deviation
String imageStdDevStr = "Std Dev (R,G,B): " + String.format("%.4g", imageRedStdDev) + ", " + String.format("%.4g", imageGreenStdDev) + ", " + String.format("%.4g", imageBlueStdDev);
canvas.drawText(imageStdDevStr, marginWidth+10-1, 60-1, mPaintBlack);
canvas.drawText(imageStdDevStr, marginWidth+10+1, 60-1, mPaintBlack);
canvas.drawText(imageStdDevStr, marginWidth+10+1, 60+1, mPaintBlack);
canvas.drawText(imageStdDevStr, marginWidth+10-1, 60+1, mPaintBlack);
canvas.drawText(imageStdDevStr, marginWidth+10, 60, mPaintYellow);
// Draw red intensity histogram
float barMaxHeight = 3000;
float barWidth = ((float)newImageWidth) / 256;
float barMarginHeight = 2;
RectF barRect = new RectF();
barRect.bottom = canvasHeight - 200;
barRect.left = marginWidth;
barRect.right = barRect.left + barWidth;
for (int bin = 0; bin < 256; bin++)
{
float prob = (float)mRedHistogram[bin] / (float)redHistogramSum;
barRect.top = barRect.bottom -
Math.min(80,prob*barMaxHeight) - barMarginHeight;
canvas.drawRect(barRect, mPaintBlack);
barRect.top += barMarginHeight;
canvas.drawRect(barRect, mPaintRed);
barRect.left += barWidth;
barRect.right += barWidth;
} // bin
// Draw green intensity histogram
barRect.bottom = canvasHeight - 100;
barRect.left = marginWidth;
barRect.right = barRect.left + barWidth;
for (int bin = 0; bin < 256; bin++)
{
barRect.top = barRect.bottom - Math.min(80, ((float)mGreenHistogram[bin])/((float)greenHistogramSum) * barMaxHeight) - barMarginHeight;
canvas.drawRect(barRect, mPaintBlack);
barRect.top += barMarginHeight;
canvas.drawRect(barRect, mPaintGreen);
barRect.left += barWidth;
barRect.right += barWidth;
} // bin
// Draw blue intensity histogram
barRect.bottom = canvasHeight;
barRect.left = marginWidth;
barRect.right = barRect.left + barWidth;
for (int bin = 0; bin < 256; bin++)
{
barRect.top = barRect.bottom - Math.min(80, ((float)mBlueHistogram[bin])/((float)blueHistogramSum) * barMaxHeight) - barMarginHeight;
canvas.drawRect(barRect, mPaintBlack);
barRect.top += barMarginHeight;
canvas.drawRect(barRect, mPaintBlue);
barRect.left += barWidth;
barRect.right += barWidth;
} // bin
} // end if statement
super.onDraw(canvas);
} // end onDraw method
static public void decodeYUV420SP(int[] rgb, byte[] yuv420sp, int width, int height) {
final int frameSize = width * height;
for (int j = 0, yp = 0; j < height; j++) {
int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
for (int i = 0; i < width; i++, yp++) {
int y = (0xff & ((int) yuv420sp[yp])) - 16;
if (y < 0) y = 0;
if ((i & 1) == 0) {
v = (0xff & yuv420sp[uvp++]) - 128;
u = (0xff & yuv420sp[uvp++]) - 128;
}
int y1192 = 1192 * y;
int r = (y1192 + 1634 * v);
int g = (y1192 - 833 * v - 400 * u);
int b = (y1192 + 2066 * u);
if (r < 0) r = 0; else if (r > 262143) r = 262143;
if (g < 0) g = 0; else if (g > 262143) g = 262143;
if (b < 0) b = 0; else if (b > 262143) b = 262143;
rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
}
}
}
static public void decodeYUV420SPGrayscale(int[] rgb, byte[] yuv420sp, int width, int height)
{
final int frameSize = width * height;
for (int pix = 0; pix < frameSize; pix++)
{
int pixVal = (0xff & ((int) yuv420sp[pix])) - 16;
if (pixVal < 0) pixVal = 0;
if (pixVal > 255) pixVal = 255;
rgb[pix] = 0xff000000 | (pixVal << 16) | (pixVal << 8) | pixVal;
} // pix
}
static public void calculateIntensityHistogram(int[] rgb, int[] histogram, int width, int height, int component)
{
for (int bin = 0; bin < 256; bin++)
{
histogram[bin] = 0;
} // bin
if (component == 0) // red
{
for (int pix = 0; pix < width*height; pix += 3)
{
int pixVal = (rgb[pix] >> 16) & 0xff;
histogram[ pixVal ]++;
} // pix
}
else if (component == 1) // green
{
for (int pix = 0; pix < width*height; pix += 3)
{
int pixVal = (rgb[pix] >> 8) & 0xff;
histogram[ pixVal ]++;
} // pix
}
else // blue
{
for (int pix = 0; pix < width*height; pix += 3)
{
int pixVal = rgb[pix] & 0xff;
histogram[ pixVal ]++;
} // pix
}
}
}
// ----------------------------------------------------------------------
class Preview extends SurfaceView implements SurfaceHolder.Callback {
SurfaceHolder mHolder;
Camera mCamera;
DrawOnTop mDrawOnTop;
boolean mFinished;
Preview(Context context, DrawOnTop drawOnTop) {
super(context);
mDrawOnTop = drawOnTop;
mFinished = false;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
mCamera = Camera.open();
try {
mCamera.setPreviewDisplay(holder);
// Preview callback used whenever new viewfinder frame is available
mCamera.setPreviewCallback(new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera)
{
if ( (mDrawOnTop == null) || mFinished )
return;
if (mDrawOnTop.mBitmap == null)
{
// Initialize the draw-on-top companion
Camera.Parameters params = camera.getParameters();
mDrawOnTop.mImageWidth = params.getPreviewSize().width;
mDrawOnTop.mImageHeight = params.getPreviewSize().height;
mDrawOnTop.mBitmap = Bitmap.createBitmap(mDrawOnTop.mImageWidth,
mDrawOnTop.mImageHeight, Bitmap.Config.RGB_565);
mDrawOnTop.mRGBData = new int[mDrawOnTop.mImageWidth * mDrawOnTop.mImageHeight];
mDrawOnTop.mYUVData = new byte[data.length];
}
// Pass YUV data to draw-on-top companion
System.arraycopy(data, 0, mDrawOnTop.mYUVData, 0, data.length);
mDrawOnTop.invalidate();
}
});
}
catch (IOException exception) {
mCamera.release();
mCamera = null;
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
// Because the CameraDevice object is not a shared resource, it's very
// important to release it when the activity is paused.
mFinished = true;
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
mCamera.release();
mCamera = null;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(320, 240);
parameters.setPreviewFrameRate(15);
parameters.setSceneMode(Camera.Parameters.SCENE_MODE_NIGHT);
parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
mCamera.setParameters(parameters);
mCamera.startPreview();
}
答案 0 :(得分：0)
大量直接绘制到屏幕上。通常，绘制到位图的速度更快，然后只需将位图传输到onDraw中的屏幕即可。此外，你的onDraw是巨大的 - 你希望它小而快，尽可能提前完成尽可能多的计算。您还希望避免在onDraw中实例化对象或从中调用的任何函数 - 这需要时间。
基本上代码是有效的，但不是为了提高效率而编写的。学校项目的典型内容（是的，包括由TA /教授编写的大部分代码），