canvas 旋转后图像模糊，仅在 Android 6
Blurry image after canvas rotate, only in Android 6
我有一个自定义视图，代码如下：
private final Drawable outerGauge;
private final Drawable innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
innerGauge.draw(canvas);
canvas.rotate(-rotation, rotateX, rotateY);
}
大多数情况下，这会生成非常清晰的图像。然而，有时结果看起来像这样：
这似乎只发生在我的两个测试设备之一上。该设备是摩托罗拉 moto G，具有 Android 6 升级。另一个似乎总是能产生非常清晰图像的测试设备是 Oneplus X，Android 5。它也不一致，有时会发生，然后下一刻又不会。根据我的测试，它甚至不依赖于应用的旋转量。不过，我从未见过它发生在直角（0、90、180 度）上，而且在接近 45 或 135 度的角度上它似乎更糟。
有问题的图像是导入的 SVG，直接放在 res/drawable 文件夹中。因此它不可能是决议。 （此外，gauge_outer 被放置在完全相同的文件夹中并以完全相同的方式制作，尽管这个并没有变得模糊。）
关于如何解决这个问题有什么想法吗？
编辑：
好吧，别管我说的完全不一致了。它似乎完全一致，并且当旋转越来越接近 90 度时最差。另外，只要旋转正好 90 度，指示器就会完全消失。
编辑：
看：两个模拟器，一个 运行 Android 5 和一个 运行 Android 6:
完整源码如下：
package nl.dvandenberg.gauge;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
public class GaugeView extends View {
private static final int ORIGINAL_ROTATE_Y = 510;
private static final int ORIGINAL_IMAGE_HEIGHT = 613;
private static final int ORIGINAL_IMAGE_WIDTH = 1046;
private final Drawable outerGauge;
private final Drawable innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
}
public GaugeView(Context context) {
super(context);
setProgress(48);
}
public GaugeView(Context context, AttributeSet attrs) {
super(context, attrs);
setProgress(48);
}
public GaugeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setProgress(48);
}
public void setProgress(double percentage) {
this.rotation = (int) (180 * Math.min(100, Math.max(0, percentage)) / 100);
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
double width = MeasureSpec.getSize(widthMeasureSpec);
double idealHeight = ORIGINAL_IMAGE_HEIGHT * width / ORIGINAL_IMAGE_WIDTH;
double height = Math.min(idealHeight, MeasureSpec.getSize(heightMeasureSpec));
width = width * height / idealHeight;
heightMeasureSpec = MeasureSpec.makeMeasureSpec((int) height, MeasureSpec.getMode(heightMeasureSpec));
rotateX = (float) (width / 2f);
rotateY = (float) (height / ORIGINAL_IMAGE_HEIGHT * ORIGINAL_ROTATE_Y);
outerGauge.setBounds(0, 0, (int) width, (int) height);
innerGauge.setBounds(0, 0, (int) width, (int) height);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
innerGauge.draw(canvas);
}
}
和drawable/gauge_inner.xml
<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
android:width="1046dp"
android:height="613dp"
android:viewportWidth="1046"
android:viewportHeight="613">
<path
android:fillColor="#aa3939"
android:pathData="M142.541,516.071 C145.053,517.623,156.088,519.334,183.255,522.586
C203.832,525.024,251.438,530.676,289.03,535.184
C326.708,539.641,359.782,543.523,362.537,543.896
C365.292,544.268,388.127,547.018,413.445,550.067 L459.289,555.468
L462.946,560.401 C468.075,567.485,479.691,577.405,489.255,582.968
C499.701,589.062,520.069,594.737,531.817,594.883
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C333.904,466.9,293.067,471.772,249.427,476.991
C205.788,482.211,164.951,487.082,158.678,487.817
C144.122,489.408,139.036,491.998,136.796,498.719
C134.433,505.626,136.72,512.388,142.541,516.07 Z" />
</vector>
和drawable/gauge_outer.xml
<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
android:width="1046dp"
android:height="613dp"
android:viewportWidth="1046"
android:viewportHeight="613">
<path
android:fillColor="#aa3939"
android:pathData="M488.981,0.56719 C465.882,2.06727,430.783,6.96753,412.984,11.0677
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C231.691,63.4706,113.696,164.376,49.898,299.183
C16.6993,369.187,0,444.491,0,523.495
C0,540.296,0.0999961,541.696,1.99992,543.596
C3.99984,545.596,5.29979,545.596,59.4977,545.596
C113.696,545.596,114.996,545.596,116.995,543.596
C118.895,541.696,118.995,540.296,118.995,522.595
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C555.278,0.16716,507.68,-0.63288,488.981,0.56719 Z" />
</vector>
虽然不是答案，但我设法找到了解决方法。此解决方法依赖于将图像绘制到链接到位图的 canvas 上，然后在 onDraw 方法中将其绘制到最终旋转的 canvas 上。
似乎这个问题真的只出现在 nodpi-drawables 上，换句话说，导入的 svg。然而，它非常一致。无论形状是多路径矢量还是简单的正方形都没有关系，问题总是采用完全相同的形状，当 canvas 旋转 90° 时图像完全消失。
我用来绕过这个问题的完整代码如下：
package nl.dvandenberg.energymonitor.customViews;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
import nl.dvandenberg.energymonitor.R;
public class GaugeView extends View {
private static final int ORIGINAL_ROTATE_Y = 510;
private static final int ORIGINAL_IMAGE_HEIGHT = 613;
private static final int ORIGINAL_IMAGE_WIDTH = 1046;
private final Drawable outerGauge, innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
private Bitmap innerGaugeBitmap;
private final Canvas innerGaugeCanvas;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
innerGaugeCanvas = new Canvas();
}
public GaugeView(Context context) {
super(context);
}
public GaugeView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public GaugeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public void setProgress(double percentage) {
this.rotation = (int) (180 * Math.min(100, Math.max(0, percentage)) / 100);
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
double width = MeasureSpec.getSize(widthMeasureSpec);
double idealHeight = ORIGINAL_IMAGE_HEIGHT * width / ORIGINAL_IMAGE_WIDTH;
double height = Math.min(idealHeight, MeasureSpec.getSize(heightMeasureSpec));
width = width * height / idealHeight;
heightMeasureSpec = MeasureSpec.makeMeasureSpec((int) height, MeasureSpec.getMode(heightMeasureSpec));
rotateX = (float) (width / 2f);
rotateY = (float) (height / ORIGINAL_IMAGE_HEIGHT * ORIGINAL_ROTATE_Y);
outerGauge.setBounds(0, 0, (int) width, (int) height);
innerGauge.setBounds(0, 0, (int) width, (int) height);
if (innerGaugeBitmap != null){
innerGaugeBitmap.recycle();
}
innerGaugeBitmap = Bitmap.createBitmap((int) width, (int) height, Bitmap.Config.ARGB_8888); // Gives LINT-warning draw-allocation, but no other way to upscale bitmaps exists.
innerGaugeCanvas.setBitmap(innerGaugeBitmap);
innerGaugeBitmap.eraseColor(Color.TRANSPARENT);
innerGauge.draw(innerGaugeCanvas);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onDraw(Canvas canvas) {
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
canvas.drawBitmap(innerGaugeBitmap,0,0,null);
}
}
重要的部分出现在 onMeasure 方法中：
if (innerGaugeBitmap != null){
innerGaugeBitmap.recycle();
}
innerGaugeBitmap = Bitmap.createBitmap((int) width, (int) height, Bitmap.Config.ARGB_8888); // Gives LINT-warning draw-allocation, but no other way to upscale bitmaps exists.
innerGaugeCanvas.setBitmap(innerGaugeBitmap);
innerGaugeBitmap.eraseColor(Color.TRANSPARENT);
innerGauge.draw(innerGaugeCanvas);
我已在 https://code.google.com/p/android/issues/detail?id=208453
提交错误报告
我有一个自定义视图，代码如下：
private final Drawable outerGauge;
private final Drawable innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
innerGauge.draw(canvas);
canvas.rotate(-rotation, rotateX, rotateY);
}
大多数情况下，这会生成非常清晰的图像。然而，有时结果看起来像这样：
有问题的图像是导入的 SVG，直接放在 res/drawable 文件夹中。因此它不可能是决议。 （此外，gauge_outer 被放置在完全相同的文件夹中并以完全相同的方式制作，尽管这个并没有变得模糊。）
关于如何解决这个问题有什么想法吗？
编辑：
好吧，别管我说的完全不一致了。它似乎完全一致，并且当旋转越来越接近 90 度时最差。另外，只要旋转正好 90 度，指示器就会完全消失。
编辑：
看：两个模拟器，一个 运行 Android 5 和一个 运行 Android 6:
完整源码如下：
package nl.dvandenberg.gauge;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
public class GaugeView extends View {
private static final int ORIGINAL_ROTATE_Y = 510;
private static final int ORIGINAL_IMAGE_HEIGHT = 613;
private static final int ORIGINAL_IMAGE_WIDTH = 1046;
private final Drawable outerGauge;
private final Drawable innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
}
public GaugeView(Context context) {
super(context);
setProgress(48);
}
public GaugeView(Context context, AttributeSet attrs) {
super(context, attrs);
setProgress(48);
}
public GaugeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setProgress(48);
}
public void setProgress(double percentage) {
this.rotation = (int) (180 * Math.min(100, Math.max(0, percentage)) / 100);
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
double width = MeasureSpec.getSize(widthMeasureSpec);
double idealHeight = ORIGINAL_IMAGE_HEIGHT * width / ORIGINAL_IMAGE_WIDTH;
double height = Math.min(idealHeight, MeasureSpec.getSize(heightMeasureSpec));
width = width * height / idealHeight;
heightMeasureSpec = MeasureSpec.makeMeasureSpec((int) height, MeasureSpec.getMode(heightMeasureSpec));
rotateX = (float) (width / 2f);
rotateY = (float) (height / ORIGINAL_IMAGE_HEIGHT * ORIGINAL_ROTATE_Y);
outerGauge.setBounds(0, 0, (int) width, (int) height);
innerGauge.setBounds(0, 0, (int) width, (int) height);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
innerGauge.draw(canvas);
}
}
和drawable/gauge_inner.xml
<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
android:width="1046dp"
android:height="613dp"
android:viewportWidth="1046"
android:viewportHeight="613">
<path
android:fillColor="#aa3939"
android:pathData="M142.541,516.071 C145.053,517.623,156.088,519.334,183.255,522.586
C203.832,525.024,251.438,530.676,289.03,535.184
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C365.292,544.268,388.127,547.018,413.445,550.067 L459.289,555.468
L462.946,560.401 C468.075,567.485,479.691,577.405,489.255,582.968
C499.701,589.062,520.069,594.737,531.817,594.883
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C144.122,489.408,139.036,491.998,136.796,498.719
C134.433,505.626,136.72,512.388,142.541,516.07 Z" />
</vector>
和drawable/gauge_outer.xml
<?xml version="1.0" encoding="utf-8"?>
<vector xmlns:android="http://schemas.android.com/apk/res/android"
android:width="1046dp"
android:height="613dp"
android:viewportWidth="1046"
android:viewportHeight="613">
<path
android:fillColor="#aa3939"
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C16.6993,369.187,0,444.491,0,523.495
C0,540.296,0.0999961,541.696,1.99992,543.596
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虽然不是答案，但我设法找到了解决方法。此解决方法依赖于将图像绘制到链接到位图的 canvas 上，然后在 onDraw 方法中将其绘制到最终旋转的 canvas 上。
似乎这个问题真的只出现在 nodpi-drawables 上，换句话说，导入的 svg。然而，它非常一致。无论形状是多路径矢量还是简单的正方形都没有关系，问题总是采用完全相同的形状，当 canvas 旋转 90° 时图像完全消失。
我用来绕过这个问题的完整代码如下：
package nl.dvandenberg.energymonitor.customViews;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
import nl.dvandenberg.energymonitor.R;
public class GaugeView extends View {
private static final int ORIGINAL_ROTATE_Y = 510;
private static final int ORIGINAL_IMAGE_HEIGHT = 613;
private static final int ORIGINAL_IMAGE_WIDTH = 1046;
private final Drawable outerGauge, innerGauge;
private float rotateX;
private float rotateY;
private int rotation = 0;
private Bitmap innerGaugeBitmap;
private final Canvas innerGaugeCanvas;
{
outerGauge = getContext().getDrawable(R.drawable.gauge_outer);
innerGauge = getContext().getDrawable(R.drawable.gauge_inner);
innerGaugeCanvas = new Canvas();
}
public GaugeView(Context context) {
super(context);
}
public GaugeView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public GaugeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public void setProgress(double percentage) {
this.rotation = (int) (180 * Math.min(100, Math.max(0, percentage)) / 100);
invalidate();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
double width = MeasureSpec.getSize(widthMeasureSpec);
double idealHeight = ORIGINAL_IMAGE_HEIGHT * width / ORIGINAL_IMAGE_WIDTH;
double height = Math.min(idealHeight, MeasureSpec.getSize(heightMeasureSpec));
width = width * height / idealHeight;
heightMeasureSpec = MeasureSpec.makeMeasureSpec((int) height, MeasureSpec.getMode(heightMeasureSpec));
rotateX = (float) (width / 2f);
rotateY = (float) (height / ORIGINAL_IMAGE_HEIGHT * ORIGINAL_ROTATE_Y);
outerGauge.setBounds(0, 0, (int) width, (int) height);
innerGauge.setBounds(0, 0, (int) width, (int) height);
if (innerGaugeBitmap != null){
innerGaugeBitmap.recycle();
}
innerGaugeBitmap = Bitmap.createBitmap((int) width, (int) height, Bitmap.Config.ARGB_8888); // Gives LINT-warning draw-allocation, but no other way to upscale bitmaps exists.
innerGaugeCanvas.setBitmap(innerGaugeBitmap);
innerGaugeBitmap.eraseColor(Color.TRANSPARENT);
innerGauge.draw(innerGaugeCanvas);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
protected void onDraw(Canvas canvas) {
outerGauge.draw(canvas);
canvas.rotate(rotation, rotateX, rotateY);
canvas.drawBitmap(innerGaugeBitmap,0,0,null);
}
}
重要的部分出现在 onMeasure 方法中：
if (innerGaugeBitmap != null){
innerGaugeBitmap.recycle();
}
innerGaugeBitmap = Bitmap.createBitmap((int) width, (int) height, Bitmap.Config.ARGB_8888); // Gives LINT-warning draw-allocation, but no other way to upscale bitmaps exists.
innerGaugeCanvas.setBitmap(innerGaugeBitmap);
innerGaugeBitmap.eraseColor(Color.TRANSPARENT);
innerGauge.draw(innerGaugeCanvas);
我已在 https://code.google.com/p/android/issues/detail?id=208453
提交错误报告