android图片叠加方法

Android有时候会遇到需要两张图片叠加起来的效果，现记录如下：

/**此方法分别传入两个bitmap对象，一个为底图(背景图background)，*另一个则位于其上面(前景图foreground)，若上面的bitmap是不透明的话，*就会完全遮住下面的bitmap，那么保存为图片后，就只能看到位于上面的bitmap的信息，*图片的大小为两个bitmap叠加的大小。*/    private Bitmap toConformBitmap(Bitmap background, Bitmap foreground) {        if( background == null ) {            return null;        }        int bgWidth = background.getWidth();        int bgHeight = background.getHeight();        //create the new blank bitmap 创建一个新的和SRC长度宽度一样的位图        Bitmap newbmp = Bitmap.createBitmap(bgWidth, bgHeight, Bitmap.Config.ARGB_8888);        Canvas cv = new Canvas(newbmp);        //draw bg into        //在 0，0坐标开始画入bg        cv.drawBitmap(background, 0, 0, null);        //draw fg into        Paint paint = new Paint();        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));        //在 0，0坐标开始画入fg ，可以从任意位置画入        cv.drawBitmap(foreground, 0, 1000, paint);        //save all clip        paint.setXfermode(null);        return newbmp;    }

/**保存bitmap为一张图片：*/private String saveBitmap(Bitmap bitmap) {        String  imagePath = getApplication().getFilesDir().getAbsolutePath() + "/temp.png";                File file = new File(imagePath);        if(file.exists()) {            file.delete();        }        try{            FileOutputStream out = new FileOutputStream(file);            if(bitmap.compress(Bitmap.CompressFormat.PNG, 100, out)){                out.flush();                out.close();            }             } catch (Exception e) {            Toast.makeText(this, "保存失败, 1).show();            e.printStackTrace();        }        return imagePath;    }

另外有从其他博客上看到的方法，包括上下叠加，左右拼接和上下拼接。

    /*     * 把两个位图覆盖合成为一个位图，以底层位图的长宽为基准     * @param backBitmap 在底部的位图     * @param frontBitmap 盖在上面的位图     * @return     */    public static Bitmap mergeBitmap(Bitmap backBitmap, Bitmap frontBitmap) {        if (backBitmap == null || backBitmap.isRecycled()                 || frontBitmap == null || frontBitmap.isRecycled()) {            Log.e(TAG, "backBitmap=" + backBitmap + ";frontBitmap=" + frontBitmap);            return null;        }        Bitmap bitmap = backBitmap.copy(Config.ARGB_8888, true);        Canvas canvas = new Canvas(bitmap);        Rect baseRect  = new Rect(0, 0, backBitmap.getWidth(), backBitmap.getHeight());        Rect frontRect = new Rect(0, 0, frontBitmap.getWidth(), frontBitmap.getHeight());        canvas.drawBitmap(frontBitmap, frontRect, baseRect, null);        return bitmap;    }    /**     * 把两个位图覆盖合成为一个位图，左右拼接     * @param leftBitmap      * @param rightBitmap      * @param isBaseMax 是否以宽度大的位图为准，true则小图等比拉伸，false则大图等比压缩     * @return     */    public static Bitmap mergeBitmap_LR(Bitmap leftBitmap, Bitmap rightBitmap, boolean isBaseMax) {        if (leftBitmap == null || leftBitmap.isRecycled()                 || rightBitmap == null || rightBitmap.isRecycled()) {            JDLog.logError(TAG, "leftBitmap=" + leftBitmap + ";rightBitmap=" + rightBitmap);            return null;        }        int height = 0; // 拼接后的高度，按照参数取大或取小        if (isBaseMax) {            height = leftBitmap.getHeight() > rightBitmap.getHeight() ? leftBitmap.getHeight() : rightBitmap.getHeight();        } else {            height = leftBitmap.getHeight() < rightBitmap.getHeight() ? leftBitmap.getHeight() : rightBitmap.getHeight();        }        // 缩放之后的bitmap        Bitmap tempBitmapL = leftBitmap;        Bitmap tempBitmapR = rightBitmap;        if (leftBitmap.getHeight() != height) {            tempBitmapL = Bitmap.createScaledBitmap(leftBitmap, (int)(leftBitmap.getWidth()*1f/leftBitmap.getHeight()*height), height, false);        } else if (rightBitmap.getHeight() != height) {            tempBitmapR = Bitmap.createScaledBitmap(rightBitmap, (int)(rightBitmap.getWidth()*1f/rightBitmap.getHeight()*height), height, false);        }        // 拼接后的宽度        int width = tempBitmapL.getWidth() + tempBitmapR.getWidth();        // 定义输出的bitmap        Bitmap bitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);        Canvas canvas = new Canvas(bitmap);        // 缩放后两个bitmap需要绘制的参数        Rect leftRect = new Rect(0, 0, tempBitmapL.getWidth(), tempBitmapL.getHeight());        Rect rightRect  = new Rect(0, 0, tempBitmapR.getWidth(), tempBitmapR.getHeight());        // 右边图需要绘制的位置，往右边偏移左边图的宽度，高度是相同的        Rect rightRectT  = new Rect(tempBitmapL.getWidth(), 0, width, height);        canvas.drawBitmap(tempBitmapL, leftRect, leftRect, null);        canvas.drawBitmap(tempBitmapR, rightRect, rightRectT, null);        return bitmap;    }    /**     * 把两个位图覆盖合成为一个位图，上下拼接     * @param leftBitmap      * @param rightBitmap      * @param isBaseMax 是否以高度大的位图为准，true则小图等比拉伸，false则大图等比压缩     * @return     */    public static Bitmap mergeBitmap_TB(Bitmap topBitmap, Bitmap bottomBitmap, boolean isBaseMax) {        if (topBitmap == null || topBitmap.isRecycled()                 || bottomBitmap == null || bottomBitmap.isRecycled()) {            JDLog.logError(TAG, "topBitmap=" + topBitmap + ";bottomBitmap=" + bottomBitmap);            return null;        }        int width = 0;        if (isBaseMax) {            width = topBitmap.getWidth() > bottomBitmap.getWidth() ? topBitmap.getWidth() : bottomBitmap.getWidth();        } else {            width = topBitmap.getWidth() < bottomBitmap.getWidth() ? topBitmap.getWidth() : bottomBitmap.getWidth();        }        Bitmap tempBitmapT = topBitmap;        Bitmap tempBitmapB = bottomBitmap;        if (topBitmap.getWidth() != width) {            tempBitmapT = Bitmap.createScaledBitmap(topBitmap, width, (int)(topBitmap.getHeight()*1f/topBitmap.getWidth()*width), false);        } else if (bottomBitmap.getWidth() != width) {            tempBitmapB = Bitmap.createScaledBitmap(bottomBitmap, width, (int)(bottomBitmap.getHeight()*1f/bottomBitmap.getWidth()*width), false);        }        int height = tempBitmapT.getHeight() + tempBitmapB.getHeight();        Bitmap bitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888);        Canvas canvas = new Canvas(bitmap);        Rect topRect = new Rect(0, 0, tempBitmapT.getWidth(), tempBitmapT.getHeight());        Rect bottomRect  = new Rect(0, 0, tempBitmapB.getWidth(), tempBitmapB.getHeight());        Rect bottomRectT  = new Rect(0, tempBitmapT.getHeight(), width, height);        canvas.drawBitmap(tempBitmapT, topRect, topRect, null);        canvas.drawBitmap(tempBitmapB, bottomRect, bottomRectT, null);        return bitmap;    }
此方法只是两张图片的简单叠加拼接，而我们可能还需要一些更加复杂的叠加效果，所以android提供了16种叠加效果，请看下一篇！