【移動(dòng)應(yīng)用開發(fā)技術(shù)】Android開發(fā)中如何實(shí)現(xiàn)圖片灰階顯示

【移動(dòng)應(yīng)用開發(fā)技術(shù)】Android開發(fā)中如何實(shí)現(xiàn)圖片灰階顯示

這篇文章將為大家詳細(xì)講解有關(guān)Android開發(fā)中如何實(shí)現(xiàn)圖片灰階顯示，在下覺得挺實(shí)用的，因此分享給大家做個(gè)參考，希望大家閱讀完這篇文章后可以有所收獲。

灰階顯示圖片的典型應(yīng)用就是用戶頭像，如用戶在線頭像顯示彩色（原圖），不在線顯示灰色（黑白圖）?？偨Y(jié)一點(diǎn)就是更加一張?jiān)紙D片來通過顏色的過濾處理計(jì)算得到不同顯示效果的圖片。這方法的API主要位于：android.

使用上文中提到的“三種算法轉(zhuǎn)換彩色灰階”一文中提到的灰階計(jì)算方法產(chǎn)生的黑白圖片顯示效果如下圖：

說明：通過UseMatrix是使用Android的ColorMatrix和ColorFilter實(shí)現(xiàn)，其中設(shè)置ColorMatrix的setSaturation(floatsat)飽和度設(shè)置為0時(shí)顏色過濾之后顯示灰階，android.graphics.ColorMatrix的內(nèi)部實(shí)現(xiàn)和具體RGB顏色權(quán)重值近似等于圖中BT709中的權(quán)重。

代碼示例（依賴此文中附加的灰階計(jì)算方法封裝類）

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_grayscale);

ButterKnife.bind(this);

BitmapDrawable

bd

=

(BitmapDrawable)

Original_ImageView.getDrawable();

Bitmap

bitmap

=

bd.getBitmap();

Log.d(TAG,

"

w="

+

bitmap.getWidth()

+

",

h="

+

bitmap.getHeight()

+

",

c="

+

bitmap.getConfig().toString());

//0

BT709

Bitmap

matrix

=

Bitmap.createBitmap(bitmap.getWidth(),

bitmap.getHeight(),

Bitmap.Config.ARGB_8888);

Canvas

canvas

=

new

Canvas(matrix);

Paint

paint

=

new

Paint();

ColorMatrix

colorMatrix

=

new

ColorMatrix();

//傳入一個(gè)大于1的數(shù)字將增加飽和度，而傳入一個(gè)0～1之間的數(shù)字會(huì)減少飽和度。0值將產(chǎn)生一幅灰度圖像

//Android

ColorMatrix

默認(rèn)的灰階計(jì)算采用下面的BT709標(biāo)準(zhǔn)

colorMatrix.setSaturation(0f);

ColorMatrixColorFilter

colorMatrixColorFilter

=

new

ColorMatrixColorFilter(colorMatrix);

paint.setColorFilter(colorMatrixColorFilter);

canvas.drawBitmap(bitmap,

0f,

0f,

paint);

Matrix_ImageView.setImageBitmap(matrix);

//原始圖片

Bitmap

sunflower

=

XUtils.BitmapUtil.decodeMutableBitmapFromResourceId(this,

R.drawable.sunflower);

//1

Bitmap

lightness

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.Lightness);

Lightness_ImageView.setImageBitmap(lightness);

//2

Bitmap

average

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.Average);

Average_ImageView.setImageBitmap(average);

//3

Bitmap

luminosity

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.Luminosity);

Luminosity_ImageView.setImageBitmap(luminosity);

//4

Bitmap

bt709

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.BT709);

BT709_ImageView.setImageBitmap(bt709);

//5

Bitmap

rmy

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.RMY);

RMY_ImageView.setImageBitmap(rmy);

//6

Bitmap

y

=

grayScale(sunflower,

XUtils.GrayScaleUtil.GrayScale.Y);

Y_ImageView.setImageBitmap(y);

}

public

Bitmap

grayScale(final

Bitmap

bitmap,

XUtils.GrayScaleUtil.GrayScale

grayScale)

{

if

(null

==

bitmap

||

null

==

grayScale)

{

return

null;

}

Bitmap

rs

=

Bitmap.createBitmap(bitmap.getWidth(),

bitmap.getHeight(),

Bitmap.Config.ARGB_8888);

Canvas

canvas

=

new

Canvas(rs);

Paint

paint

=

new

Paint();

for

(int

x

=

0,

w

=

bitmap.getWidth();

x

<

w;

x++)

{

for

(int

y

=

0,

h

=

bitmap.getHeight();

y

<

h;

y++)

{

int

c

=

bitmap.getPixel(x,

y);

int

a

=

Color.alpha(c);

int

r

=

Color.red(c);

int

g

=

Color.red(c);

int

b

=

Color.blue(c);

int

gc

=

grayScale.grayScale(r,

g,

b);

paint.setColor(Color.argb(a,

gc,

gc,

gc));