Android中Bitmap和Drawable 心已赠人 2022-08-05 00:34 136阅读 0赞 ### 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。还有ColorDrawable对象,用于将color生成Drawable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 #### Java代码 ![收藏代码][icon_star.png] 1. Resources res = getResources(); 2. Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon); #### 2、Bitmap → byte\[\] #### Java代码 ![收藏代码][icon_star.png] 1. **public** **byte**\[\] Bitmap2Bytes(Bitmap bm) \{ 2. ByteArrayOutputStream baos = **new** ByteArrayOutputStream(); 3. bm.compress(Bitmap.CompressFormat.PNG, 100, baos); 4. **return** baos.toByteArray(); 5. \} #### 3、byte\[\] → Bitmap #### Java代码 ![收藏代码][icon_star.png] 1. **public** Bitmap Bytes2Bimap(**byte**\[\] b) \{ 2. **if** (b.length != 0) \{ 3. **return** BitmapFactory.decodeByteArray(b, 0, b.length); 4. \} **else** \{ 5. **return** **null**; 6. \} 7. \} #### 4、Bitmap缩放 #### Java代码 ![收藏代码][icon_star.png] 1. **public** **static** Bitmap zoomBitmap(Bitmap bitmap, **int** width, **int** height) \{ 2. **int** w = bitmap.getWidth(); 3. **int** h = bitmap.getHeight(); 4. Matrix matrix = **new** Matrix(); 5. **float** scaleWidth = ((**float**) width / w); 6. **float** scaleHeight = ((**float**) height / h); 7. matrix.postScale(scaleWidth, scaleHeight); 8. Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, **true**); 9. **return** newbmp; 10. \} #### 5、将Drawable转化为Bitmap #### Java代码 ![收藏代码][icon_star.png] 1. **public** **static** Bitmap drawableToBitmap(Drawable drawable) \{ 2. // 取 drawable 的长宽 3. **int** w = drawable.getIntrinsicWidth(); 4. **int** h = drawable.getIntrinsicHeight(); 5. 6. // 取 drawable 的颜色格式 7. Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB\_8888 8. : Bitmap.Config.RGB\_565; 9. // 建立对应 bitmap 10. Bitmap bitmap = Bitmap.createBitmap(w, h, config); 11. // 建立对应 bitmap 的画布 12. Canvas canvas = **new** Canvas(bitmap); 13. drawable.setBounds(0, 0, w, h); 14. // 把 drawable 内容画到画布中 15. drawable.draw(canvas); 16. **return** bitmap; 17. \} #### 6、获得圆角图片 #### Java代码 ![收藏代码][icon_star.png] 1. **public** **static** Bitmap getRoundedCornerBitmap(Bitmap bitmap, **float** roundPx) \{ 2. **int** w = bitmap.getWidth(); 3. **int** h = bitmap.getHeight(); 4. Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB\_8888); 5. Canvas canvas = **new** Canvas(output); 6. **final** **int** color = 0xff424242; 7. **final** Paint paint = **new** Paint(); 8. **final** Rect rect = **new** Rect(0, 0, w, h); 9. **final** RectF rectF = **new** RectF(rect); 10. paint.setAntiAlias(**true**); 11. canvas.drawARGB(0, 0, 0, 0); 12. paint.setColor(color); 13. canvas.drawRoundRect(rectF, roundPx, roundPx, paint); 14. paint.setXfermode(**new** PorterDuffXfermode(Mode.SRC\_IN)); 15. canvas.drawBitmap(bitmap, rect, rect, paint); 16. 17. **return** output; 18. \} #### 7、获得带倒影的图片 #### Java代码 ![收藏代码][icon_star.png] 1. **public** **static** Bitmap createReflectionImageWithOrigin(Bitmap bitmap) \{ 2. **final** **int** reflectionGap = 4; 3. **int** w = bitmap.getWidth(); 4. **int** h = bitmap.getHeight(); 5. 6. Matrix matrix = **new** Matrix(); 7. matrix.preScale(1, -1); 8. 9. Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w, 10. h / 2, matrix, **false**); 11. 12. Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2), 13. Config.ARGB\_8888); 14. 15. Canvas canvas = **new** Canvas(bitmapWithReflection); 16. canvas.drawBitmap(bitmap, 0, 0, **null**); 17. Paint deafalutPaint = **new** Paint(); 18. canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint); 19. 20. canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, **null**); 21. 22. Paint paint = **new** Paint(); 23. LinearGradient shader = **new** LinearGradient(0, bitmap.getHeight(), 0, 24. bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff, 25. 0x00ffffff, TileMode.CLAMP); 26. paint.setShader(shader); 27. // Set the Transfer mode to be porter duff and destination in 28. paint.setXfermode(**new** PorterDuffXfermode(Mode.DST\_IN)); 29. // Draw a rectangle using the paint with our linear gradient 30. canvas.drawRect(0, h, w, bitmapWithReflection.getHeight() 31. + reflectionGap, paint); 32. 33. **return** bitmapWithReflection; 34. \} ### 三、Drawable ### #### 1、Bitmap转换成Drawable #### Java代码 ![收藏代码][icon_star.png] 1. Bitmap bm=xxx; //xxx根据你的情况获取 2. BitmapDrawable bd= **new** BitmapDrawable(getResource(), bm); 3. 因为BtimapDrawable是Drawable的子类,最终直接使用bd对象即可。 #### 2、Drawable缩放 #### Java代码 ![收藏代码][icon_star.png] 1. **public** **static** Drawable zoomDrawable(Drawable drawable, **int** w, **int** h) \{ 2. **int** width = drawable.getIntrinsicWidth(); 3. **int** height = drawable.getIntrinsicHeight(); 4. // drawable转换成bitmap 5. Bitmap oldbmp = drawableToBitmap(drawable); 6. // 创建操作图片用的Matrix对象 7. Matrix matrix = **new** Matrix(); 8. // 计算缩放比例 9. **float** sx = ((**float**) w / width); 10. **float** sy = ((**float**) h / height); 11. // 设置缩放比例 12. matrix.postScale(sx, sy); 13. // 建立新的bitmap,其内容是对原bitmap的缩放后的图 14. Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height, 15. matrix, **true**); 16. **return** **new** BitmapDrawable(newbmp); 17. \} [icon_star.png]: /images/20220805/8f166657065745b4ae007464ba57d08d.png
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