Android中Bitmap和Drawable

一、相關概念

1、Drawable就是一個可畫的對象，其可能是一張位圖（BitmapDrawable），也可能是一個圖形（ShapeDrawable），還有可能是一個圖層（LayerDrawable），我們根據畫圖的需求，創建相應的可畫對象

2、Canvas畫布，繪圖的目的區域，用於繪圖

3、Bitmap位圖，用於圖的處理

4、Matrix矩陣

二、Bitmap
1、從資源中獲取Bitmap
Java代碼 收藏代碼

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


2、Bitmap → byte[]
Java代碼 收藏代碼

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

3、byte[] → Bitmap
Java代碼 收藏代碼

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

4、Bitmap縮放
Java代碼 收藏代碼

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、將Drawable轉化爲Bitmap
Java代碼 收藏代碼

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

// 取 drawable 的顏色格式
Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
// 建立對應 bitmap
Bitmap bitmap = Bitmap.createBitmap(w, h, config);
// 建立對應 bitmap 的畫布
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, w, h);
// 把 drawable 內容畫到畫布中
drawable.draw(canvas);
return bitmap;
}

6、獲得圓角圖片
Java代碼 收藏代碼

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、獲得帶倒影的圖片
Java代碼 收藏代碼

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 in
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
// Draw a rectangle using the paint with our linear gradient
canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()
+ reflectionGap, paint);

return bitmapWithReflection;
}

三、Drawable
1、Bitmap轉換成Drawable
Java代碼 收藏代碼

Bitmap bm=xxx; //xxx根據你的情況獲取
BitmapDrawable bd= new BitmapDrawable(getResource(), bm);
因爲BtimapDrawable是Drawable的子類，最終直接使用bd對象即可。

2、Drawable縮放
Java代碼 收藏代碼

public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();
// drawable轉換成bitmap
Bitmap oldbmp = drawableToBitmap(drawable);
// 創建操作圖片用的Matrix對象
Matrix matrix = new Matrix();
// 計算縮放比例
float sx = ((float) w / width);
float sy = ((float) h / height);
// 設置縮放比例
matrix.postScale(sx, sy);
// 建立新的bitmap，其內容是對原bitmap的縮放後的圖
Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
matrix, true);
return new BitmapDrawable(newbmp);
}