drawable与bitmap
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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、Bitmap
1、从资源中获取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 bitmapBitmap 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、获得带倒影的图片
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 = 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 + reflectionGap, 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 Transfer 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
1、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。
2、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 / 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);}
3、牺牲图片质量为代价,将图片进行放缩
BitmapFactory.Options opts = new BitmapFactory.Options();opts.inJustDecodeBounds = true;Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
设置inJustDecodeBounds为true后,decodeFile并不分配空间,但可计算出原始图片的长度和宽度,即opts.width和opts.height。有了这两个参数,再通过一定的算法,即可得到一个恰当的inSampleSize。Android提供了一种动态计算的方法。如下:
public static int computeSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { int initialSize = computeInitialSampleSize(options, minSideLength, maxNumOfPixels); int roundedSize; if (initialSize <= 8) { roundedSize = 1; while (roundedSize < initialSize) { roundedSize <<= 1; } } else { roundedSize = (initialSize + 7) / 8 * 8; } return roundedSize;} private static int computeInitialSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { double w = options.outWidth; double h = options.outHeight; int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels)); int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(Math.floor(w / minSideLength), Math.floor(h / minSideLength)); if (upperBound < lowerBound) { return lowerBound; } if ((maxNumOfPixels == -1) && (minSideLength == -1)) { return 1; } else if (minSideLength == -1) { return lowerBound; } else { return upperBound; }}
我们只需要使用此函数就行了:
BitmapFactory.Options opts = new BitmapFactory.Options();opts.inJustDecodeBounds = true;BitmapFactory.decodeFile(imageFile, opts); opts.inSampleSize = computeSampleSize(opts, -1, 128*128);//这里一定要将其设置回false,因为之前我们将其设置成了true opts.inJustDecodeBounds = false;try { Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts); imageView.setImageBitmap(bmp); } catch (OutOfMemoryError err) { }
4、创建临时空间
当在android设备中载入较大图片资源时,可以创建一些临时空间,将载入的资源载入到临时空间中。
BitmapFactory.Options bfOptions=new BitmapFactory.Options(); bfOptions.inDither=false; bfOptions.inPurgeable=true; bfOptions.inTempStorage=new byte[12 * 1024]; // bfOptions.inJustDecodeBounds = true; File file = new File(pePicFile.getAbsolutePath() + "/"+info.getImage()); FileInputStream fs=null; try { fs = new FileInputStream(file); } catch (FileNotFoundException e) { e.printStackTrace(); } Bitmap bmp = null; if(fs != null) try { bmp = BitmapFactory.decodeFileDescriptor(fs.getFD(), null, bfOptions); } catch (IOException e) { e.printStackTrace(); }finally{ if(fs!=null) { try { fs.close(); } catch (IOException e) { e.printStackTrace(); } } }
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