目标是能够在拍摄的图像上书写/绘制/绘制任何内容，并在不破坏图像的情况下进行擦除，使图像保持完整，并且在保存图像时，图形和背景图像将是包含在最终输出中。
我已经构建了一个应用程序，可以拍摄照片，然后将其发送到新的活动进行预览和编辑，我可以在这里绘制图像，如圆圈或某些线条。我能够通过创建位图并将其传递给新的Canvas（）构造函数来完成此任务。
这个问题是我可以在图像上写字但是当我使用擦除模式时图像也会被删除，我想实现一些可以让我擦除而不会破坏背景图像的东西，同时最后保存图像时，仍会包含背景图像。
我的观点代码如下。
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
public class DrawingView extends View {
//drawing path
private Path drawPath;
//drawing and canvas paint
private Paint drawPaint, canvasPaint;
//initial color
private int paintColor = 0xFF660000, paintAlpha = 255;
//canvas
private Canvas drawCanvas;
//canvas bitmap
private Bitmap canvasBitmap;
//brush sizes
private float brushSize, lastBrushSize;
//erase flag
private boolean erase=false;
Bitmap bg;
public DrawingView(Context context, AttributeSet attrs){
super(context, attrs);
setupDrawing();
}
//setup drawing
private void setupDrawing(){
//prepare for drawing and setup paint stroke properties
brushSize = getResources().getInteger(R.integer.medium_size);
lastBrushSize = brushSize;
drawPath = new Path();
drawPaint = new Paint();
drawPaint.setColor(paintColor);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(brushSize);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
Resources res = getResources();
Bitmap bitmap = BitmapFactory.decodeResource(res, R.drawable.background);
bg = bitmap.copy(Bitmap.Config.ARGB_8888, true);
}
//size assigned to view
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(bg);
}
//draw the view - will be called after touch event
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(bg, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
}
//register user touches as drawing action
@Override
public boolean onTouchEvent(MotionEvent event) {
float touchX = event.getX();
float touchY = event.getY();
//respond to down, move and up events
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawPath.lineTo(touchX, touchY);
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
//redraw
invalidate();
return true;
}
//update color
public void setColor(String newColor){
invalidate();
//check whether color value or pattern name
if(newColor.startsWith("#")){
paintColor = Color.parseColor(newColor);
drawPaint.setColor(paintColor);
drawPaint.setShader(null);
}
else{
//pattern
int patternID = getResources().getIdentifier(
newColor, "drawable", "com.example.drawingfun");
//decode
Bitmap patternBMP = BitmapFactory.decodeResource(getResources(), patternID);
//create shader
BitmapShader patternBMPshader = new BitmapShader(patternBMP,
Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
//color and shader
drawPaint.setColor(0xFFFFFFFF);
drawPaint.setShader(patternBMPshader);
}
}
//set brush size
public void setBrushSize(float newSize){
float pixelAmount = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
newSize, getResources().getDisplayMetrics());
brushSize=pixelAmount;
drawPaint.setStrokeWidth(brushSize);
}
//get and set last brush size
public void setLastBrushSize(float lastSize){
lastBrushSize=lastSize;
}
public float getLastBrushSize(){
return lastBrushSize;
}
//set erase true or false
public void setErase(boolean isErase){
erase=isErase;
drawPaint.setColor(Color.parseColor("#FFFFFF"));
if(erase) drawPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
else drawPaint.setXfermode(null);
drawPaint.setColor(paintColor);
}
//start new drawing
public void startNew(){
drawCanvas.drawColor(0, PorterDuff.Mode.CLEAR);
invalidate();
}
//return current alpha
public int getPaintAlpha(){
return Math.round((float)paintAlpha/255*100);
}
//set alpha
public void setPaintAlpha(int newAlpha){
paintAlpha=Math.round((float)newAlpha/100*255);
drawPaint.setColor(paintColor);
drawPaint.setAlpha(paintAlpha);
}
}
MainActivity.java就是这个
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;
import android.widget.Toast;
import java.util.UUID;
public class MainActivity extends Activity implements OnClickListener {
//custom drawing view
private DrawingView drawView;
//buttons
private ImageButton currPaint, drawBtn, eraseBtn, newBtn, saveBtn, opacityBtn;
//sizes
private float smallBrush, mediumBrush, largeBrush;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//get drawing view
drawView = (DrawingView)findViewById(R.id.drawing);
// if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
// drawView.setBackground(getResources().getDrawable(R.drawable.background, null));
// }
// else
// drawView.setBackground(getResources().getDrawable(R.drawable.background));
//get the palette and first color button
LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
currPaint = (ImageButton)paintLayout.getChildAt(0);
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
//sizes from dimensions
smallBrush = getResources().getInteger(R.integer.small_size);
mediumBrush = getResources().getInteger(R.integer.medium_size);
largeBrush = getResources().getInteger(R.integer.large_size);
//draw button
drawBtn = (ImageButton)findViewById(R.id.draw_btn);
drawBtn.setOnClickListener(this);
//set initial size
drawView.setBrushSize(smallBrush);
//erase button
eraseBtn = (ImageButton)findViewById(R.id.erase_btn);
eraseBtn.setOnClickListener(this);
//new button
newBtn = (ImageButton)findViewById(R.id.new_btn);
newBtn.setOnClickListener(this);
//save button
saveBtn = (ImageButton)findViewById(R.id.save_btn);
saveBtn.setOnClickListener(this);
//opacity
opacityBtn = (ImageButton)findViewById(R.id.opacity_btn);
opacityBtn.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
// getMenuInflater().inflate(R.menu.main, menu);
return true;
}
//user clicked paint
public void paintClicked(View view){
//use chosen color
//set erase false
drawView.setErase(false);
drawView.setPaintAlpha(100);
drawView.setBrushSize(drawView.getLastBrushSize());
if(view!=currPaint){
ImageButton imgView = (ImageButton)view;
String color = view.getTag().toString();
drawView.setColor(color);
//update ui
imgView.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint));
currPaint=(ImageButton)view;
}
}
@Override
public void onClick(View view){
if(view.getId()==R.id.draw_btn){
//draw button clicked
final Dialog brushDialog = new Dialog(this);
brushDialog.setTitle("Brush size:");
brushDialog.setContentView(R.layout.brush_chooser);
//listen for clicks on size buttons
ImageButton smallBtn = (ImageButton)brushDialog.findViewById(R.id.small_brush);
smallBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(smallBrush);
drawView.setLastBrushSize(smallBrush);
brushDialog.dismiss();
}
});
ImageButton mediumBtn = (ImageButton)brushDialog.findViewById(R.id.medium_brush);
mediumBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(mediumBrush);
drawView.setLastBrushSize(mediumBrush);
brushDialog.dismiss();
}
});
ImageButton largeBtn = (ImageButton)brushDialog.findViewById(R.id.large_brush);
largeBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(false);
drawView.setBrushSize(largeBrush);
drawView.setLastBrushSize(largeBrush);
brushDialog.dismiss();
}
});
//show and wait for user interaction
brushDialog.show();
}
else if(view.getId()==R.id.erase_btn){
//switch to erase - choose size
final Dialog brushDialog = new Dialog(this);
brushDialog.setTitle("Eraser size:");
brushDialog.setContentView(R.layout.brush_chooser);
//size buttons
ImageButton smallBtn = (ImageButton)brushDialog.findViewById(R.id.small_brush);
smallBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(smallBrush);
brushDialog.dismiss();
}
});
ImageButton mediumBtn = (ImageButton)brushDialog.findViewById(R.id.medium_brush);
mediumBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(mediumBrush);
brushDialog.dismiss();
}
});
ImageButton largeBtn = (ImageButton)brushDialog.findViewById(R.id.large_brush);
largeBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setErase(true);
drawView.setBrushSize(largeBrush);
brushDialog.dismiss();
}
});
brushDialog.show();
}
else if(view.getId()==R.id.new_btn){
//new button
AlertDialog.Builder newDialog = new AlertDialog.Builder(this);
newDialog.setTitle("New drawing");
newDialog.setMessage("Start new drawing (you will lose the current drawing)?");
newDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
drawView.startNew();
dialog.dismiss();
}
});
newDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
dialog.cancel();
}
});
newDialog.show();
}
else if(view.getId()==R.id.save_btn){
//save drawing
AlertDialog.Builder saveDialog = new AlertDialog.Builder(this);
saveDialog.setTitle("Save drawing");
saveDialog.setMessage("Save drawing to device Gallery?");
saveDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
//save drawing
drawView.setDrawingCacheEnabled(true);
//attempt to save
String imgSaved = MediaStore.Images.Media.insertImage(
getContentResolver(), drawView.getDrawingCache(),
UUID.randomUUID().toString()+".png", "drawing");
//feedback
if(imgSaved!=null){
Toast savedToast = Toast.makeText(getApplicationContext(),
"Drawing saved to Gallery!", Toast.LENGTH_SHORT);
savedToast.show();
}
else{
Toast unsavedToast = Toast.makeText(getApplicationContext(),
"Oops! Image could not be saved.", Toast.LENGTH_SHORT);
unsavedToast.show();
}
drawView.destroyDrawingCache();
}
});
saveDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int which){
dialog.cancel();
}
});
saveDialog.show();
}
else if(view.getId()==R.id.opacity_btn){
//launch opacity chooser
final Dialog seekDialog = new Dialog(this);
seekDialog.setTitle("Opacity level:");
seekDialog.setContentView(R.layout.opacity_chooser);
//get ui elements
final TextView seekTxt = (TextView)seekDialog.findViewById(R.id.opq_txt);
final SeekBar seekOpq = (SeekBar)seekDialog.findViewById(R.id.opacity_seek);
//set max
seekOpq.setMax(100);
//show current level
int currLevel = drawView.getPaintAlpha();
seekTxt.setText(currLevel+"%");
seekOpq.setProgress(currLevel);
//update as user interacts
seekOpq.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
seekTxt.setText(Integer.toString(progress)+"%");
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {}
});
//listen for clicks on ok
Button opqBtn = (Button)seekDialog.findViewById(R.id.opq_ok);
opqBtn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
drawView.setPaintAlpha(seekOpq.getProgress());
seekDialog.dismiss();
}
});
//show dialog
seekDialog.show();
}
}
}
答案 0 :(得分：1)
你已经以正确的方式实现了所有的事情，但我只是建议你尝试下面的代码，可能会帮助你。
public void clearCanvas() {
drawPath.reset();
invalidate();
}
尝试此方法而不是setErase（），上述方法用于清除使用touch创建的路径。您可以在此方法中将所有值重置为默认值。
答案 1 :(得分：0)
解决了我的问题只是通过setBackgroundDrawable将图像设置为surfaceview的背景。然后保存它我只需要从画布获取绘图缓存，然后包括背景图像。