Android开发——Bitmap,byte[],Drawable相互转化

这几天开发中，遇到一个问题需要对Camera获取到的byte[] data进行转化为Bitmap,现做一笔记。

在surfaceview中结合Camera获取到摄像头图像，这段代码是我程序中的一部分

@Override
public void onPreviewFrame(final byte[] data, Camera camera) {
camera.setPreviewCallback(null);

if (mCamera == null)
return;

Camera.Parameters parameters = camera.getParameters();
int width = parameters.getPreviewSize().width;
int height = parameters.getPreviewSize().height;

YuvImage yuv = new YuvImage(data, parameters.getPreviewFormat(), width, height, null);

ByteArrayOutputStream out = new ByteArrayOutputStream();
yuv.compressToJpeg(new Rect(0, 0, width, height), 50, out);

byte[] bytes = out.toByteArray();
final Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

this.mCamera.setPreviewCallback(this);
}

现在对三者具体如何互相转换做一说明：

准备：概念说明

1、Drawable就是一个可画的对象,其可能是一张位图(BitmapDrawable),也可能是一个图形(ShapeDrawable),还有可能是一个图层(LayerDrawable),我们根据画图的需求，创建相应的可画对象

2、Canvas画布，绘图的目的区域，用于绘图

3、Bitmap位图，用于图的处理

4、Matrix矩阵 ,图像矩阵

1.从resources中获取Bitmap

Resources res = getResources();
Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);

2.Bitmap → byte[]

public byte[] Bitmap2Bytes(Bitmap bm) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
return baos.toByteArray();
}

3.byte[] → Bitmap

public Bitmap Bytes2Bimap(byte[] b) {
if (b.length != 0) {
return BitmapFactory.decodeByteArray(b, 0, b.length);
} else {
return null;
}
}

4.Bitmap缩放

public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Matrix matrix = new Matrix();
float scaleWidth = ((float) width / w);
float scaleHeight = ((float) height / h);
matrix.postScale(scaleWidth, scaleHeight);
Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
return newbmp;
}

5.将Drawable转化为Bitmap

public static Bitmap drawableToBitmap(Drawable drawable) {
// 取 drawable 的长宽
int w = drawable.getIntrinsicWidth();
int h = drawable.getIntrinsicHeight();

// 取 drawable 的颜色格式
Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
// 建立对应 bitmap
Bitmap bitmap = Bitmap.createBitmap(w, h, config);
// 建立对应 bitmap 的画布
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, w, h);
// 把 drawable 内容画到画布中
drawable.draw(canvas);
return bitmap;
}

6.获得圆角图片

public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, w, h);
final RectF rectF = new RectF(rect);
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);

return output;
}

7.Bitmap转换成Drawable

Bitmap bm=xxx; //xxx根据你的情况获取
BitmapDrawable bd= new BitmapDrawable(getResource(), bm);
//因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。

8.Drawable缩放

public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();
// drawable转换成bitmap
Bitmap oldbmp = drawableToBitmap(drawable);
// 创建操作图片用的Matrix对象
Matrix matrix = new Matrix();
// 计算缩放比例
float sx = ((float) w / width);
float sy = ((float) h / height);
// 设置缩放比例
matrix.postScale(sx, sy);
// 建立新的bitmap，其内容是对原bitmap的缩放后的图
Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,matrix, true);
return new BitmapDrawable(newbmp);
}