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本篇文章給大家分享的是有關怎么在Android中利用ImageView將圖片進行圓形、圓角處理，小編覺得挺實用的，因此分享給大家學習，希望大家閱讀完這篇文章后可以有所收獲，話不多說，跟著小編一起來看看吧。
基本思路是，自定義一個ImageView，通過重寫onDraw方法畫出一個圓形的圖片來：
public class ImageViewPlus extends ImageView{
private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
private Bitmap mRawBitmap;
private BitmapShader mShader;
private Matrix mMatrix = new Matrix();
public ImageViewPlus(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onDraw(Canvas canvas) {
Bitmap rawBitmap = getBitmap(getDrawable());
if (rawBitmap != null){
int viewWidth = getWidth();
int viewHeight = getHeight();
int viewMinSize = Math.min(viewWidth, viewHeight);
float dstWidth = viewMinSize;
float dstHeight = viewMinSize;
if (mShader == null || !rawBitmap.equals(mRawBitmap)){
mRawBitmap = rawBitmap;
mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
}
if (mShader != null){
mMatrix.setScale(dstWidth / rawBitmap.getWidth(), dstHeight / rawBitmap.getHeight());
mShader.setLocalMatrix(mMatrix);
}
mPaintBitmap.setShader(mShader);
float radius = viewMinSize / 2.0f;
canvas.drawCircle(radius, radius, radius, mPaintBitmap);
} else {
super.onDraw(canvas);
}
}
private Bitmap getBitmap(Drawable drawable){
if (drawable instanceof BitmapDrawable){
return ((BitmapDrawable)drawable).getBitmap();
} else if (drawable instanceof ColorDrawable){
Rect rect = drawable.getBounds();
int width = rect.right - rect.left;
int height = rect.bottom - rect.top;
int color = ((ColorDrawable)drawable).getColor();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
return bitmap;
} else {
return null;
}
}
}分析一下代碼：
canvas.drawCircle 決定了畫出來的形狀是圓形，而圓形的內容則是通過 mPaintBitmap.setShader 搞定的。
其中，BitmapShader需要設置Bitmap填充ImageView的方式(CLAMP：拉伸邊緣, MIRROR：鏡像, REPEAT：整圖重復)。
這里其實設成什么不重要，因為我們實際需要的是將Bitmap按比例縮放成跟ImageView一樣大，而不是預置的三種效果。
所以，別忘了 mMatrix.setScale 和 mShader.setLocalMatrix 一起用，將圖片縮放一下。
四、支持邊框
public class ImageViewPlus extends ImageView{
private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
private Bitmap mRawBitmap;
private BitmapShader mShader;
private Matrix mMatrix = new Matrix();
private float mBorderWidth = dip2px(15);
private int mBorderColor = 0xFF0080FF;
public ImageViewPlus(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onDraw(Canvas canvas) {
Bitmap rawBitmap = getBitmap(getDrawable());
if (rawBitmap != null){
int viewWidth = getWidth();
int viewHeight = getHeight();
int viewMinSize = Math.min(viewWidth, viewHeight);
float dstWidth = viewMinSize;
float dstHeight = viewMinSize;
if (mShader == null || !rawBitmap.equals(mRawBitmap)){
mRawBitmap = rawBitmap;
mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
}
if (mShader != null){
mMatrix.setScale((dstWidth - mBorderWidth * 2) / rawBitmap.getWidth(), (dstHeight - mBorderWidth * 2) / rawBitmap.getHeight());
mShader.setLocalMatrix(mMatrix);
}
mPaintBitmap.setShader(mShader);
mPaintBorder.setStyle(Paint.Style.STROKE);
mPaintBorder.setStrokeWidth(mBorderWidth);
mPaintBorder.setColor(mBorderColor);
float radius = viewMinSize / 2.0f;
canvas.drawCircle(radius, radius, radius - mBorderWidth / 2.0f, mPaintBorder);
canvas.translate(mBorderWidth, mBorderWidth);
canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
} else {
super.onDraw(canvas);
}
}
private Bitmap getBitmap(Drawable drawable){
if (drawable instanceof BitmapDrawable){
return ((BitmapDrawable)drawable).getBitmap();
} else if (drawable instanceof ColorDrawable){
Rect rect = drawable.getBounds();
int width = rect.right - rect.left;
int height = rect.bottom - rect.top;
int color = ((ColorDrawable)drawable).getColor();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
return bitmap;
} else {
return null;
}
}
private int dip2px(int dipVal)
{
float scale = getResources().getDisplayMetrics().density;
return (int)(dipVal * scale + 0.5f);
}
}看代碼中，加邊框實際上就是用實心純色的 Paint 畫了一個圓邊，在此基礎上畫上原來的頭像即可。
需要的注意的地方有三個：
1)、圓框的半徑不是 radius ，而應該是 radius - mBorderWidth / 2.0f 。想象著拿著筆去畫線，線其實是畫在右圖中白色圈的位置，只不過它很粗。
2)、在ImageView大小不變的基礎上，頭像的實際大小要比沒有邊框的時候小了，所以 mMatrix.setScale 的時候要把邊框的寬度去掉。
3)、畫頭像Bitmap的時候不能直接 canvas.drawCircle(radius, radius, radius - mBorderWidth, mPaintBitmap) ，這樣你會發現頭像的右側和下方邊緣被拉伸了（右圖）
為什么呢？因為 Paint 默認是以左上角為基準開始繪制的，此時頭像的實際區域是右圖中的紅框，而超過紅框的部分（圓形的右側和下方），自然被 TileMode.CLAMP效果沿邊緣拉伸了。
所以，需要通過挪動坐標系的位置和調整圓心，才能把頭像畫在正確的區域（右圖綠框）中。
五、更多玩法 —— 支持xml配置
既然有了邊框，那如果想配置邊框的寬度和顏色該如何是好呢？
基本上兩個思路：
1)、給ImageViewPlus加上set接口，設置完成之后通過 invalidate(); 重繪一下即可；
2)、在xml里就支持配置一些自定義屬性，這樣用起來會方便很多。
這里重點說一下支持xml配置自定義屬性。
自定義控件要支持xml配置自定義屬性的話，首先需要在 \res\values 里去定義屬性：
<?xml version="1.0" encoding="utf-8"?> <resources> <attr name="borderColor" format="color" /> <attr name="borderWidth" format="dimension" /> <declare-styleable name="ImageViewPlus"> <attr name="borderColor" /> <attr name="borderWidth" /> </declare-styleable> </resources>
然后在ImageViewPlus的構造函數中去讀取這些自定義屬性：
private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
private static final int DEFAULT_BORDER_WIDTH = 0;
public ImageViewPlus(Context context, AttributeSet attrs) {
super(context, attrs);
//取xml文件中設定的參數
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
ta.recycle();
}在xml布局中使用自定義屬性：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/wallpaper"
android:orientation="vertical"
tools:context="${relativePackage}.${activityClass}" >
<cc.snser.imageviewplus.ImageViewPlus
android:id="@+id/imgplus"
android:layout_width="200dp"
android:layout_height="300dp"
android:layout_marginBottom="50dp"
android:layout_centerHorizontal="true"
android:layout_alignParentBottom="true"
android:src="@drawable/img_square"
snser:borderColor="#FF0080FF"
snser:borderWidth="15dp" />
</RelativeLayout>六、 圓角ImageView
其實原理上一樣，把 canvas.drawCircle 對應改成 canvas.drawRoundRect 就OK了，直接貼代碼吧：
public class ImageViewPlus extends ImageView{
/**
* android.widget.ImageView
*/
public static final int TYPE_NONE = 0;
/**
* 圓形
*/
public static final int TYPE_CIRCLE = 1;
/**
* 圓角矩形
*/
public static final int TYPE_ROUNDED_RECT = 2;
private static final int DEFAULT_TYPE = TYPE_NONE;
private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;
private static final int DEFAULT_BORDER_WIDTH = 0;
private static final int DEFAULT_RECT_ROUND_RADIUS = 0;
private int mType;
private int mBorderColor;
private int mBorderWidth;
private int mRectRoundRadius;
private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);
private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);
private RectF mRectBorder = new RectF();
private RectF mRectBitmap = new RectF();
private Bitmap mRawBitmap;
private BitmapShader mShader;
private Matrix mMatrix = new Matrix();
public ImageViewPlus(Context context, AttributeSet attrs) {
super(context, attrs);
//取xml文件中設定的參數
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);
mType = ta.getInt(R.styleable.ImageViewPlus_type, DEFAULT_TYPE);
mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);
mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));
mRectRoundRadius = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_rectRoundRadius, dip2px(DEFAULT_RECT_ROUND_RADIUS));
ta.recycle();
}
@Override
protected void onDraw(Canvas canvas) {
Bitmap rawBitmap = getBitmap(getDrawable());
if (rawBitmap != null && mType != TYPE_NONE){
int viewWidth = getWidth();
int viewHeight = getHeight();
int viewMinSize = Math.min(viewWidth, viewHeight);
float dstWidth = mType == TYPE_CIRCLE ? viewMinSize : viewWidth;
float dstHeight = mType == TYPE_CIRCLE ? viewMinSize : viewHeight;
float halfBorderWidth = mBorderWidth / 2.0f;
float doubleBorderWidth = mBorderWidth * 2;
if (mShader == null || !rawBitmap.equals(mRawBitmap)){
mRawBitmap = rawBitmap;
mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);
}
if (mShader != null){
mMatrix.setScale((dstWidth - doubleBorderWidth) / rawBitmap.getWidth(), (dstHeight - doubleBorderWidth) / rawBitmap.getHeight());
mShader.setLocalMatrix(mMatrix);
}
mPaintBitmap.setShader(mShader);
mPaintBorder.setStyle(Paint.Style.STROKE);
mPaintBorder.setStrokeWidth(mBorderWidth);
mPaintBorder.setColor(mBorderWidth > 0 ? mBorderColor : Color.TRANSPARENT);
if (mType == TYPE_CIRCLE){
float radius = viewMinSize / 2.0f;
canvas.drawCircle(radius, radius, radius - halfBorderWidth, mPaintBorder);
canvas.translate(mBorderWidth, mBorderWidth);
canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);
} else if (mType == TYPE_ROUNDED_RECT){
mRectBorder.set(halfBorderWidth, halfBorderWidth, dstWidth - halfBorderWidth, dstHeight - halfBorderWidth);
mRectBitmap.set(0.0f, 0.0f, dstWidth - doubleBorderWidth, dstHeight - doubleBorderWidth);
float borderRadius = mRectRoundRadius - halfBorderWidth > 0.0f ? mRectRoundRadius - halfBorderWidth : 0.0f;
float bitmapRadius = mRectRoundRadius - mBorderWidth > 0.0f ? mRectRoundRadius - mBorderWidth : 0.0f;
canvas.drawRoundRect(mRectBorder, borderRadius, borderRadius, mPaintBorder);
canvas.translate(mBorderWidth, mBorderWidth);
canvas.drawRoundRect(mRectBitmap, bitmapRadius, bitmapRadius, mPaintBitmap);
}
} else {
super.onDraw(canvas);
}
}
private int dip2px(int dipVal)
{
float scale = getResources().getDisplayMetrics().density;
return (int)(dipVal * scale + 0.5f);
}
private Bitmap getBitmap(Drawable drawable){
if (drawable instanceof BitmapDrawable){
return ((BitmapDrawable)drawable).getBitmap();
} else if (drawable instanceof ColorDrawable){
Rect rect = drawable.getBounds();
int width = rect.right - rect.left;
int height = rect.bottom - rect.top;
int color = ((ColorDrawable)drawable).getColor();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));
return bitmap;
} else {
return null;
}
}
}<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/wallpaper"
android:orientation="vertical"
tools:context="${relativePackage}.${activityClass}" >
<cc.snser.imageviewplus.ImageViewPlus
android:id="@+id/imgplus"
android:layout_width="200dp"
android:layout_height="300dp"
android:layout_marginBottom="50dp"
android:layout_centerHorizontal="true"
android:layout_alignParentBottom="true"
android:src="@drawable/img_rectangle"
snser:type="rounded_rect"
snser:borderColor="#FF0080FF"
snser:borderWidth="10dp"
snser:rectRoundRadius="30dp" />
</RelativeLayout><?xml version="1.0" encoding="utf-8"?> <resources> <attr name="type"> <enum name="none" value="0" /> <enum name="circle" value="1" /> <enum name="rounded_rect" value="2" /> </attr> <attr name="borderColor" format="color" /> <attr name="borderWidth" format="dimension" /> <attr name="rectRoundRadius" format="dimension" /> <declare-styleable name="ImageViewPlus"> <attr name="type" /> <attr name="borderColor" /> <attr name="borderWidth" /> <attr name="rectRoundRadius" /> </declare-styleable> </resources>
以上就是怎么在Android中利用ImageView將圖片進行圓形、圓角處理，小編相信有部分知識點可能是我們日常工作會見到或用到的。希望你能通過這篇文章學到更多知識。更多詳情敬請關注億速云行業資訊頻道。
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