android tv 大背景图加载优化
2019-10-17 本文已影响0人
ihu11
android tv 有时候需要加载全屏背景图，且背景图也很大，特别是背景图是服务器下发的，下载好存在本地。加载的时候需要异步加载，这样异步加载的时候就会先显示的是Application的默认背景图（demo是黑屏图），然后才能加载到图片，为了提高这个背景图加载的用户体验，可以先读取这个图片的部分像素的小图，然后生成一张大尺寸高斯模糊图直接加载，这个时候比加载原始大图要快得多，在性能差的设备都基本可以达到直接显示出来的效果。
先看下直接加载的效果图
device-2019-10-17-174850.gif
如果不使用先读取小图的方式效果
device-2019-10-17-175140.gif
算法详解：
public static Drawable buildBlurDrawable(Context context, String filePath) throws Exception {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 64 * 64);
opts.inJustDecodeBounds = false;
opts.inPurgeable = true;
opts.inInputShareable = true;
opts.inPreferredConfig = Bitmap.Config.ARGB_4444;
Bitmap mBitmap = BitmapFactory.decodeFile(filePath, opts);
if(mBitmap.getWidth() > 0 && mBitmap.getHeight() > 0){
Bitmap overlay = doBlurOnBackgournd(mBitmap);
mBitmap.recycle();
return new BitmapDrawable(context.getResources(), overlay);
} else {
mBitmap.recycle();
return null;
}
}
先读取了64x64像素的小图，并且使用ARGB_4444的方式节省内存，加快读取速度，读取完这张小图后使用高斯模糊再转化成原来的大图，速度很快
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
public class FastBlur {
public static Drawable buildBlurDrawable(Context context, int resId) throws Exception {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeResource(context.getResources(), resId, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 64 * 64);
opts.inJustDecodeBounds = false;
opts.inPurgeable = true;
opts.inInputShareable = true;
opts.inPreferredConfig = Bitmap.Config.ARGB_4444;
Bitmap mBitmap = BitmapFactory.decodeResource(context.getResources(),
resId, opts);
if(mBitmap.getWidth() > 0 && mBitmap.getHeight() > 0){
Bitmap overlay = doBlurOnBackgournd(mBitmap);
mBitmap.recycle();
return new BitmapDrawable(context.getResources(), overlay);
} else {
mBitmap.recycle();
return null;
}
}
public static Drawable buildBlurDrawable(Context context, String filePath) throws Exception {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, opts);
opts.inSampleSize = computeSampleSize(opts, -1, 64 * 64);
opts.inJustDecodeBounds = false;
opts.inPurgeable = true;
opts.inInputShareable = true;
opts.inPreferredConfig = Bitmap.Config.ARGB_4444;
Bitmap mBitmap = BitmapFactory.decodeFile(filePath, opts);
if(mBitmap.getWidth() > 0 && mBitmap.getHeight() > 0){
Bitmap overlay = doBlurOnBackgournd(mBitmap);
mBitmap.recycle();
return new BitmapDrawable(context.getResources(), overlay);
} else {
mBitmap.recycle();
return null;
}
}
public static Bitmap doBlurOnBackgournd(Bitmap sourceBitmap){
float scaleFactor = 1;
float radius = 5;
return doBlur(sourceBitmap, scaleFactor, radius);
}
public static Bitmap doBlur(Bitmap sourceBitmap, float scaleFactor, float radius) {
// long time1 = System.currentTimeMillis();
Bitmap overlay = Bitmap.createBitmap(
(int) (sourceBitmap.getWidth() / scaleFactor),
(int) (sourceBitmap.getHeight() / scaleFactor),
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(overlay);
// canvas.translate(-getLeft() / scaleFactor, -getTop() / scaleFactor);
canvas.scale(1 / scaleFactor, 1 / scaleFactor);
Paint paint = new Paint();
paint.setFlags(Paint.FILTER_BITMAP_FLAG);
canvas.drawBitmap(sourceBitmap, 0, 0, paint);
overlay = FastBlur.doBlur(overlay, (int) radius, true);
// long time2 = System.currentTimeMillis();
// Log.i("Catch", "time doBlur:" + (time2 - time1));
return overlay;
}
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 the larger one when there is no overlapping zone.
return lowerBound;
}
if ((maxNumOfPixels == -1) && (minSideLength == -1)) {
return 1;
} else if (minSideLength == -1) {
return lowerBound;
} else {
return upperBound;
}
}
public static Bitmap doBlur(Bitmap sentBitmap, int radius,
boolean canReuseInBitmap) {
Bitmap bitmap;
if (canReuseInBitmap) {
bitmap = sentBitmap;
} else {
bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);
}
if (radius < 1) {
return (null);
}
int w = bitmap.getWidth();
int h = bitmap.getHeight();
int[] pix = new int[w * h];
bitmap.getPixels(pix, 0, w, 0, 0, w, h);
int wm = w - 1;
int hm = h - 1;
int wh = w * h;
int div = radius + radius + 1;
int r[] = new int[wh];
int g[] = new int[wh];
int b[] = new int[wh];
int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
int vmin[] = new int[Math.max(w, h)];
int divsum = (div + 1) >> 1;
divsum *= divsum;
int dv[] = new int[256 * divsum];
for (i = 0; i < 256 * divsum; i++) {
dv[i] = (i / divsum);
}
yw = yi = 0;
int[][] stack = new int[div][3];
int stackpointer;
int stackstart;
int[] sir;
int rbs;
int r1 = radius + 1;
int routsum, goutsum, boutsum;
int rinsum, ginsum, binsum;
for (y = 0; y < h; y++) {
rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
for (i = -radius; i <= radius; i++) {
p = pix[yi + Math.min(wm, Math.max(i, 0))];
sir = stack[i + radius];
sir[0] = (p & 0xff0000) >> 16;
sir[1] = (p & 0x00ff00) >> 8;
sir[2] = (p & 0x0000ff);
rbs = r1 - Math.abs(i);
rsum += sir[0] * rbs;
gsum += sir[1] * rbs;
bsum += sir[2] * rbs;
if (i > 0) {
rinsum += sir[0];
ginsum += sir[1];
binsum += sir[2];
} else {
routsum += sir[0];
goutsum += sir[1];
boutsum += sir[2];
}
}
stackpointer = radius;
for (x = 0; x < w; x++) {
r[yi] = dv[rsum];
g[yi] = dv[gsum];
b[yi] = dv[bsum];
rsum -= routsum;
gsum -= goutsum;
bsum -= boutsum;
stackstart = stackpointer - radius + div;
sir = stack[stackstart % div];
routsum -= sir[0];
goutsum -= sir[1];
boutsum -= sir[2];
if (y == 0) {
vmin[x] = Math.min(x + radius + 1, wm);
}
p = pix[yw + vmin[x]];
sir[0] = (p & 0xff0000) >> 16;
sir[1] = (p & 0x00ff00) >> 8;
sir[2] = (p & 0x0000ff);
rinsum += sir[0];
ginsum += sir[1];
binsum += sir[2];
rsum += rinsum;
gsum += ginsum;
bsum += binsum;
stackpointer = (stackpointer + 1) % div;
sir = stack[(stackpointer) % div];
routsum += sir[0];
goutsum += sir[1];
boutsum += sir[2];
rinsum -= sir[0];
ginsum -= sir[1];
binsum -= sir[2];
yi++;
}
yw += w;
}
for (x = 0; x < w; x++) {
rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
yp = -radius * w;
for (i = -radius; i <= radius; i++) {
yi = Math.max(0, yp) + x;
sir = stack[i + radius];
sir[0] = r[yi];
sir[1] = g[yi];
sir[2] = b[yi];
rbs = r1 - Math.abs(i);
rsum += r[yi] * rbs;
gsum += g[yi] * rbs;
bsum += b[yi] * rbs;
if (i > 0) {
rinsum += sir[0];
ginsum += sir[1];
binsum += sir[2];
} else {
routsum += sir[0];
goutsum += sir[1];
boutsum += sir[2];
}
if (i < hm) {
yp += w;
}
}
yi = x;
stackpointer = radius;
for (y = 0; y < h; y++) {
// Preserve alpha channel: ( 0xff000000 & pix[yi] )
pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16)
| (dv[gsum] << 8) | dv[bsum];
rsum -= routsum;
gsum -= goutsum;
bsum -= boutsum;
stackstart = stackpointer - radius + div;
sir = stack[stackstart % div];
routsum -= sir[0];
goutsum -= sir[1];
boutsum -= sir[2];
if (x == 0) {
vmin[y] = Math.min(y + r1, hm) * w;
}
p = x + vmin[y];
sir[0] = r[p];
sir[1] = g[p];
sir[2] = b[p];
rinsum += sir[0];
ginsum += sir[1];
binsum += sir[2];
rsum += rinsum;
gsum += ginsum;
bsum += binsum;
stackpointer = (stackpointer + 1) % div;
sir = stack[stackpointer];
routsum += sir[0];
goutsum += sir[1];
boutsum += sir[2];
rinsum -= sir[0];
ginsum -= sir[1];
binsum -= sir[2];
yi += w;
}
}
bitmap.setPixels(pix, 0, w, 0, 0, w, h);
return (bitmap);
}
}
调用实现代码
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.widget.ImageView;
public class BackgroundActivity extends Activity {
Bitmap bitmap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_back);
final String imgPath = "";
ImageView img1 = findViewById(R.id.img1);
try {
img1.setBackgroundDrawable(FastBlur.buildBlurDrawable(this, imgPath));
} catch (Exception e) {
e.printStackTrace();
}
new Thread() {
public void run() {
try {
bitmap = BitmapFactory.decodeFile(imgPath);
} catch (Exception e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
ImageView img1 = findViewById(R.id.img1);
try {
img1.setImageBitmap(bitmap);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}.start();
}
}
布局代码
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/img1"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
这里使用ImageView实现的背景展示，实际加载可以使用自己项目中使用到的图片框架，比如我的项目中使用的是fresco加载的图片
public static void setDraweeBackground(Context context, SimpleDraweeView mBackgroundDrawee, String path, int width, int height) {
Uri uri = UriUtil.parseUriOrNull("file://" + path);
ImagePipeline imagePipeline = Fresco.getImagePipeline();
if (!imagePipeline.isInBitmapMemoryCache(uri)) {
try {
mBackgroundDrawee.getHierarchy().setPlaceholderImage(FastBlur.buildBlurDrawable(context, path));
} catch (Exception e) {
//TODO set default background
return;
}
}
ImageRequest request = ImageRequestBuilder.newBuilderWithSource(uri)
.setResizeOptions(new ResizeOptions(width, height)).build();
DraweeController controller = Fresco.newDraweeControllerBuilder().setImageRequest(request)
.setOldController(mBackgroundDrawee.getController()).build();
mBackgroundDrawee.setController(controller);
}
注意显示图片的时候还要注意裁剪图片到屏幕的合适尺寸，节省内存
