feat: 封面剪裁窗口使用与图片浏览窗口一致的背景颜色设置

- CropCanvasView: 将画布背景从固定的 Color.BLUE 改为支持 3 种背景类型
  (灰白棋盘格 / 全白 / 全黑)，与 ImageViewerActivity 保持一致
  - 新增 bgType 字段、setBackgroundType() / getBackgroundType() 方法
  - 新增 drawBackground() 统一绘制方法，用于 onDraw() 和 getCanvasBitmap()
  - 棋盘格使用 Drawable.draw() 渲染 Vector 到 Bitmap，再通过 BitmapShader 平铺

- CropActivity: 从 Preferences 读取保存的 bgType 并应用到画布
  - 将颜色拾取按钮替换为背景选择按钮 (ic_bg)，弹出单选对话框切换背景
  - 切换时调用 prefs.setBgType() 保存，与图片浏览窗口共享同一数据源
  - 工具栏颜色指示器随背景类型更新
  - 剪裁信息对话框改为显示背景类型名称

gallery/src/main/java/cc/winboll/studio/gallery/CropActivity.java

@@ -43,6 +43,7 @@ public class CropActivity extends AppCompatActivity {
     private int cropWidth = 240;
     private int cropHeight = 120;
     private float cropRatio = 2.0f;
+    private Preferences prefs;
     
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -54,7 +55,8 @@ public class CropActivity extends AppCompatActivity {
         cropWidth = getIntent().getIntExtra(EXTRA_CROP_WIDTH, 240);
         cropHeight = getIntent().getIntExtra(EXTRA_CROP_HEIGHT, 120);
         
-        Preferences prefs = new Preferences(this);
+        prefs = new Preferences(this);
+        int bgType = prefs.getBgType();
         if (cropWidth > 0 && cropHeight > 0) {
             cropRatio = (float) cropWidth / cropHeight;
         } else {
@@ -70,13 +72,12 @@ public class CropActivity extends AppCompatActivity {
             }
         });
         
-        final ImageView btnColorPick = findViewById(R.id.btn_color_pick);
+        final ImageView btnBg = findViewById(R.id.btn_color_pick);
-        btnColorPick.setOnClickListener(new View.OnClickListener() {
+        btnBg.setImageResource(R.drawable.ic_bg);
+        btnBg.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                boolean pickMode = !cropCanvasView.isColorPickMode();
+                showBgDialog();
-                cropCanvasView.setColorPickMode(pickMode);
-                btnColorPick.setAlpha(pickMode ? 0.5f : 1.0f);
             }
         });
         
@@ -117,39 +118,56 @@ public class CropActivity extends AppCompatActivity {
         
         final View colorView = findViewById(R.id.color_view);
         final GradientDrawable colorDrawable = (GradientDrawable) colorView.getBackground();
+        
+        cropCanvasView.setBackgroundType(bgType);
+        updateColorView(colorDrawable, bgType);
+        
         cropCanvasView.setOnBackgroundColorChangedListener(new CropCanvasView.OnBackgroundColorChangedListener() {
             @Override
             public void onBackgroundColorChanged(int color) {
-                colorDrawable.setColor(color);
             }
         });
         
-        cropCanvasView.setOnColorPickedListener(new CropCanvasView.OnColorPickedListener() {
-            @Override
-            public void onColorPicked(int color) {
-                int pickX = cropCanvasView.getLastPickImageX();
-                int pickY = cropCanvasView.getLastPickImageY();
-                colorDrawable.setColor(color);
-                Toast.makeText(CropActivity.this, 
-                    "颜色已拾取: #" + String.format("%06X", color & 0xFFFFFF) + 
-                    " (" + pickX + "," + pickY + ")", 
-                    Toast.LENGTH_SHORT).show();
-            }
-        });
-        
-        cropCanvasView.setOnColorPickEndListener(new CropCanvasView.OnColorPickEndListener() {
-            @Override
-            public void onColorPickEnd() {
-                cropCanvasView.setColorPickMode(false);
-                btnColorPick.setAlpha(1.0f);
-            }
-        });
-        
-        colorDrawable.setColor(cropCanvasView.getBackgroundColor());
-        
         loadImage();
     }
     
+    private void updateColorView(GradientDrawable drawable, int bgType) {
+        switch (bgType) {
+            case 0:
+                drawable.setColor(0xFF808080);
+                break;
+            case 1:
+                drawable.setColor(0xFFFFFFFF);
+                break;
+            case 2:
+            default:
+                drawable.setColor(0xFF000000);
+                break;
+        }
+    }
+    
+    private void showBgDialog() {
+        final String[] bgNames = {"灰白相间", "全白", "全黑"};
+        final int[] bgDrawables = {R.drawable.bg_checkerboard, R.drawable.bg_white, R.drawable.bg_black};
+        final View colorView = findViewById(R.id.color_view);
+        final GradientDrawable colorDrawable = (GradientDrawable) colorView.getBackground();
+        final int currentBgType = cropCanvasView.getBackgroundType();
+        
+        new AlertDialog.Builder(this)
+            .setTitle("选择背景")
+            .setSingleChoiceItems(bgNames, currentBgType, new android.content.DialogInterface.OnClickListener() {
+                @Override
+                public void onClick(android.content.DialogInterface dialog, int which) {
+                    cropCanvasView.setBackgroundType(which);
+                    prefs.setBgType(which);
+                    updateColorView(colorDrawable, which);
+                    dialog.dismiss();
+                }
+            })
+            .setNegativeButton("取消", null)
+            .show();
+    }
+    
     private void loadImage() {
         try {
             if (imagePath != null && new File(imagePath).exists()) {
@@ -261,7 +279,9 @@ public class CropActivity extends AppCompatActivity {
         info.append("画布宽度: ").append(cropCanvasView.getCanvasWidth()).append("px\n");
         info.append("画布高度: ").append(cropCanvasView.getCanvasHeight()).append("px\n");
         
-        info.append("\n=== 拾取颜色 ===\n");
+        info.append("\n=== 背景类型 ===\n");
+        String[] bgNames = {"灰白相间", "全白", "全黑"};
+        info.append("背景: ").append(bgNames[cropCanvasView.getBackgroundType()]).append("\n");
         int bgColor = cropCanvasView.getBackgroundColor();
         info.append("背景颜色: #").append(String.format("%06X", bgColor & 0xFFFFFF)).append("\n");
         info.append("拾取坐标: ").append(cropCanvasView.getLastPickImageX()).append(",")

gallery/src/main/java/cc/winboll/studio/gallery/CropCanvasView.java

@@ -2,11 +2,14 @@ package cc.winboll.studio.gallery;
 
 import android.content.Context;
 import android.graphics.Bitmap;
+import android.graphics.BitmapShader;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Matrix;
 import android.graphics.Paint;
 import android.graphics.RectF;
+import android.graphics.Shader;
+import android.graphics.drawable.Drawable;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.view.View;
@@ -71,6 +74,10 @@ public class CropCanvasView extends View {
     private Bitmap displayBitmap;
     private RectF initialSpanRect;
     private float initialSpan;
+    private int bgType = 2;
+    private Bitmap tileBitmap;
+    private BitmapShader tileShader;
+    private Paint bgPaint;
     private int backgroundColor = Color.BLUE;
     private boolean colorPickMode = false;
     private int previewColor = 0;
@@ -111,6 +118,60 @@ public class CropCanvasView extends View {
         cornerPaint = new Paint();
         cornerPaint.setColor(Color.WHITE);
         cornerPaint.setStyle(Paint.Style.FILL);
+        
+        bgType = 2;
+        bgPaint = new Paint();
+        initTileBitmap();
+    }
+    
+    private void initTileBitmap() {
+        if (tileBitmap != null && !tileBitmap.isRecycled()) {
+            tileBitmap.recycle();
+            tileBitmap = null;
+        }
+        tileShader = null;
+        
+        if (bgType == 0) {
+            Drawable drawable = getContext().getDrawable(R.drawable.bg_checkerboard);
+            if (drawable != null) {
+                int w = drawable.getIntrinsicWidth();
+                int h = drawable.getIntrinsicHeight();
+                if (w <= 0) w = 10;
+                if (h <= 0) h = 10;
+                tileBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
+                Canvas c = new Canvas(tileBitmap);
+                drawable.setBounds(0, 0, w, h);
+                drawable.draw(c);
+                tileShader = new BitmapShader(tileBitmap, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
+            }
+        }
+    }
+    
+    public void setBackgroundType(int type) {
+        if (bgType != type) {
+            bgType = type;
+            initTileBitmap();
+            invalidate();
+        }
+    }
+    
+    public int getBackgroundType() {
+        return bgType;
+    }
+    
+    private void drawBackground(Canvas canvas) {
+        if (bgType == 0 && tileShader != null) {
+            bgPaint.setShader(tileShader);
+            canvas.drawRect(canvasBounds, bgPaint);
+        } else if (bgType == 1) {
+            bgPaint.setShader(null);
+            bgPaint.setColor(Color.WHITE);
+            canvas.drawRect(canvasBounds, bgPaint);
+        } else {
+            bgPaint.setShader(null);
+            bgPaint.setColor(Color.BLACK);
+            canvas.drawRect(canvasBounds, bgPaint);
+        }
     }
     
     public void setImageBitmap(Bitmap bitmap) {
@@ -175,7 +236,7 @@ public class CropCanvasView extends View {
         }
         Bitmap canvasBmp = Bitmap.createBitmap(canvasWidth, canvasHeight, Bitmap.Config.ARGB_8888);
         Canvas canvas = new Canvas(canvasBmp);
-        canvas.drawColor(backgroundColor);
+        drawBackground(canvas);
         if (displayBitmap != null && !displayBitmap.isRecycled()) {
             if (displayBitmap == originalBitmap) {
                 canvas.drawBitmap(displayBitmap, imageBounds.left, imageBounds.top, imagePaint);
@@ -409,7 +470,7 @@ public class CropCanvasView extends View {
             getDisplayMatrix(matrix);
             canvas.concat(matrix);
             
-            canvas.drawColor(backgroundColor);
+            drawBackground(canvas);
             
             if (displayBitmap == originalBitmap) {
                 canvas.drawBitmap(displayBitmap, imageBounds.left, imageBounds.top, imagePaint);
@@ -523,7 +584,7 @@ public class CropCanvasView extends View {
                     if (imageBounds.contains(imgX, imgY)) {
                         previewColor = getImageColorAt(x, y);
                     } else if (canvasBounds.contains(x, y)) {
-                        previewColor = backgroundColor;
+                        previewColor = (bgType == 1) ? Color.WHITE : Color.BLACK;
                     } else {
                         previewColor = Color.TRANSPARENT;
                     }
@@ -545,7 +606,7 @@ public class CropCanvasView extends View {
                         pickedColor = colorAtPoint;
                         backgroundColor = colorAtPoint;
                     } else {
-                        pickedColor = backgroundColor;
+                        pickedColor = (bgType == 1) ? Color.WHITE : Color.BLACK;
                     }
                     if (colorPickedListener != null) {
                         colorPickedListener.onColorPicked(pickedColor);