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！