Bitmap 和 Drawable

1、Bitmap 是什么?

Bit 位 map 图

Bitmap 存储的是每一个像素点的信息

Drawable 是一个可画的对象, 可能是一个位图(BitmapDrawable), 也可能是一个图形(ShapeDrawable)

class DrawableView(context: Context?, attrs: AttributeSet?) : View(context, attrs) {
var mDrawable = MeshDrawable()
override fun onDraw(canvas: Canvas?) {
super.onDraw(canvas)
canvas ?: return
mDrawable.apply {
setBounds(0, 0, width, height)
draw(canvas)
}
}
}

2、Bitmap 和 Drawable 互转(https://corochann.com/convert-between-bitmap-and-drawable-313.html)

Bitmap to Drawable

Drawable d = new BitmapDrawable(getResources(), bitmap);

Drawable to Bitmap

public static Bitmap drawableToBitmap (Drawable drawable) {
Bitmap bitmap = null;
if (drawable instanceof BitmapDrawable) {
BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
if(bitmapDrawable.getBitmap() != null) {
return bitmapDrawable.getBitmap();
}
}
if(drawable.getIntrinsicWidth() <= 0 || drawable.getIntrinsicHeight() <= 0) {
// Single color bitmap will be created of 1x1 pixel
bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888);
} else {
bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
}
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
}

3、自定义 Drawable

自定义 Drawable 一般都是为了重用, 因为大多数时候系统提供的就够用了, 比如 ColorDrawable 等

class MeshDrawable : Drawable() {
/**
* 画笔
*/
private val mPaint by lazy {
Paint(Paint.ANTI_ALIAS_FLAG).apply {
color = Color.parseColor("#1E88E5")
strokeWidth = dp2px(3F)
}
}
private val INTERVAL by lazy { dp2px(50F).toInt() }
override fun draw(canvas: Canvas) {
// 横着画竖线
for (x in 0 until bounds.right step INTERVAL) {
canvas.drawLine(x.toFloat(), bounds.top.toFloat(), x.toFloat(), bounds.bottom.toFloat(), mPaint)
}
// 竖着画横线
for (y in 0 until bounds.bottom step INTERVAL) {
canvas.drawLine(bounds.left.toFloat(), y.toFloat(), bounds.right.toFloat(), y.toFloat(), mPaint)
}
}
override fun setAlpha(alpha: Int) {
mPaint.alpha = alpha
}
override fun getAlpha(): Int = mPaint.alpha
override fun setColorFilter(colorFilter: ColorFilter?) {
mPaint.colorFilter = colorFilter
}
override fun getColorFilter(): ColorFilter? = mPaint.colorFilter
override fun getOpacity(): Int {
return when {
mPaint.alpha == 0xff -> PixelFormat.OPAQUE
mPaint.alpha == 0 -> PixelFormat.TRANSPARENT
else -> PixelFormat.TRANSLUCENT
}
}
}

最后

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