麦子学院Android开发教程Bitmap和Drawable用法详解

1、本文章来给大家介绍Android中Bitmap和Drawable用法详解,有需要了解的同学可进入参考。一、相关概念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矩阵二、Bitmap1、从资源中获取BitmapResources res = getResources(;2、Bitmap byte代码如下public byte Bi

2、tmap2Bytes(Bitmap bm ByteArrayOutputStream baos = new ByteArrayOutputStream(;return baos.toByteArray(;3、byte Bitmap代码如下public Bitmap Bytes2Bimap(byte b if (b.length != 0 return BitmapFactory.decodeByteArray(b, 0, b.length; else return null;Bitmap缩放代码如下public static Bitmap zoomBitmap(Bitmap bitmap, i

3、nt 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

4、、将Drawable转化为Bitmap代码如下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/ 建立对应 bitmapBitmap bitmap = Bitmap.createBitmap(w, h, config;/ 建立对应 bitmap 的画布Canvas canvas = new Canvas(bitmap;d

5、rawable.setBounds(0, 0, w, h;/ 把 drawable 内容画到画布中drawable.draw(canvas;return bitmap;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

6、;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(M

7、ode.SRC_IN;canvas.drawBitmap(bitmap, rect, rect, paint;return output;6、获得圆角图片代码如下public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap final int reflectionGap = 4;int w = bitmap.getWidth(;int h = bitmap.getHeight(;Matrix matrix = new Matrix(;matrix.preScale(1, -1;Bitmap reflectionImage

8、= Bitmap.createBitmap(bitmap, 0, h / 2, w, h / 2, matrix, false;Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2, Config.ARGB_8888;Canvas canvas = new Canvas(bitmapWithReflection;canvas.drawBitmap(bitmap, 0, 0, null;Paint deafalutPaint = new Paint(;canvas.drawRect(0, h, w, h + reflect

9、ionGap, deafalutPaint;canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null;Paint paint = new Paint(;LinearGradient shader = new LinearGradient(0, bitmap.getHeight(, 0, bitmapWithReflection.getHeight( + reflectionGap, 0x70ffffff,0x00ffffff, TileMode.CLAMP;paint.setShader(shader;/ Set the Tra

10、nsfer mode to be porter duff and destination inpaint.setXfermode(new PorterDuffXfermode(Mode.DST_IN;/ Draw a rectangle using the paint with our linear gradientcanvas.drawRect(0, h, w, bitmapWithReflection.getHeight(+ reflectionGap, paint;return bitmapWithReflection;三、Drawable代码如下Bitmap bm=xxx; /xxx根

11、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。2、Drawable缩放代码如下public static Drawable zoomDrawable(Drawable drawable, int w, int h int width = drawable.getIntrinsicWidth(;int height = drawable.getIntrinsicHeight(;/ drawable转换成bitmapBitmap 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 / h