Android Bitmap 加载与像素操作，androidbitmap,Bitmap API读取
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Android Bitmap 加载与像素操作，androidbitmap,Bitmap API读取
Android Bitmap 加载与像素操作
一：加载与像素读写在Android SDK中，图像的像素读写可以通过getPixel与setPixel两个Bitmap的API实现。Bitmap API读取像素的代码如下：
int pixel = bitmap.getPixel(col, row);// ARGB int red = Color.red(pixel); // same as (pixel >> 16) &0xff int green = Color.green(pixel); // same as (pixel >> 8) &0xff int blue = Color.blue(pixel); // same as (pixel & 0xff) int alpha = Color.alpha(pixel); // same as (pixel >>> 24)
得到像素pixel是32位的整数，四个字节分别对应透明通道、红色、绿色、蓝色通道。Bitmap API 写入像素,代码如下：
bm.setPixel(col, row, Color.argb(alpha, red, green, blue));
通过Color.argb重新组装成一个int的像素值。使用BitmapFactory.decodeFile或者decodeResource等方法实现加载图像的Bitmap对象时，这些方法就会为要构建的Bitmap对象分配合适大小的内存，如果原始的图像文件数据很大，就会导致DVM不能分配请求的内存大小，从而导致OOM(out of memory)问题。而通过配置BitmapFactory.Option预先读取图像高度与宽带，图像进行适当的下采样，就可以避免OOM问题的发生。预先只获取图像高度与宽带的代码如下：
// 获取Bitmap图像大小与类型属性 BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeResource(getResources(), R.drawable.shar_03, options); int height = options.outHeight; int width = options.outWidth; String imageType = options.outMimeType;
基于下采样加载超大Bitmap图像的缩小版本：
// 下采样int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value
// that is a power of 2 and keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight
&& (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
// 获取采样后的图像显示，避免OOM问题
options.inJustDecodeBounds = false;
srcImage = BitmapFactory.decodeResource(getResources(), R.drawable.shar_03, options);二：像素操作
android彩色图像灰度化的三个简单方法
灰度化方法一：
灰度值GRAY = (max(red, green, blue) + min(red, green, blue))/2
灰度化方法二：
灰度值GRAY = (red + green + blue)/3
灰度化方法三：
灰度值GRAY = red*0.3 + green*0.59 + blue*0.11
代码实现如下：
public Bitmap gray(Bitmap bitmap, int schema)
{
Bitmap bm = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), bitmap.getConfig());
int width = bitmap.getWidth();
int height = bitmap.getHeight();
for(int row=0; row<height; row++){
for(int col=0; col<width; col++){
int pixel = bitmap.getPixel(col, row);// ARGB
int red = Color.red(pixel); // same as (pixel >> 16) &0xff
int green = Color.green(pixel); // same as (pixel >> 8) &0xff
int blue = Color.blue(pixel); // same as (pixel & 0xff)
int alpha = Color.alpha(pixel); // same as (pixel >>> 24)
int gray = 0;
if(schema == 0)
{
gray = (Math.max(blue, Math.max(red, green)) +
Math.min(blue, Math.min(red, green))) / 2;
}
else if(schema == 1)
{
gray = (red + green + blue) / 3;
}
else if(schema == 2)
{
gray = (int)(0.3 * red + 0.59 * green + 0.11 * blue);
}
bm.setPixel(col, row, Color.argb(alpha, gray, gray, gray));
}
}
return bm;
}Bitmap图像镜像映射与亮度调整的代码实现如下：
public Bitmap brightness(Bitmap bitmap, double depth)
{
Bitmap bm = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), bitmap.getConfig());
int width = bitmap.getWidth();
int height = bitmap.getHeight();
for(int row=0; row<height; row++){
for(int col=0; col<width; col++){
int pixel = bitmap.getPixel(col, row);// ARGB
int red = Color.red(pixel); // same as (pixel >> 16) &0xff
int green = Color.green(pixel); // same as (pixel >> 8) &0xff
int blue = Color.blue(pixel); // same as (pixel & 0xff)
int alpha = Color.alpha(pixel); // same as (pixel >>> 24)
double gray = (0.3 * red + 0.59 * green + 0.11 * blue);
red += (depth * gray);
if(red > 255) { red = 255; }
green += (depth * gray);
if(green > 255) { green = 255; }
blue += (depth * gray);
if(blue > 255) { blue = 255; }
bm.setPixel(col, row, Color.argb(alpha, red, green, blue));
}
}
return bm;
}
public Bitmap flip(Bitmap bitmap)
{
Bitmap bm = Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(), bitmap.getConfig());
int width = bitmap.getWidth();
int height = bitmap.getHeight();
for(int row=0; row<height; row++){
for(int col=0; col<width; col++){
int pixel = bitmap.getPixel(col, row);// ARGB
int red = Color.red(pixel); // same as (pixel >> 16) &0xff
int green = Color.green(pixel); // same as (pixel >> 8) &0xff
int blue = Color.blue(pixel); // same as (pixel & 0xff)
int alpha = Color.alpha(pixel); // same as (pixel >>> 24)
int ncol = width - col - 1;
bm.setPixel(ncol, row, Color.argb(alpha, red, green, blue));
}
}
return bm;
}运行截图：
布局XML文件内容如下：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.imageprocess1.MainActivity" > <RelativeLayout android:layout_width="wrap_content" android:layout_height="wrap_content"> <Button android:id="@+id/button_gray_3" android:layout_width="100dp" android:layout_height="wrap_content" android:text="@string/process" /> <Button android:id="@+id/button_inverse" android:layout_width="100dp" android:layout_height="wrap_content" android:layout_toRightOf="@+id/button_gray_3" android:layout_alignTop="@+id/button_gray_3" android:text="@string/inverse" /> <Button android:id="@+id/button_gray_1" android:layout_width="100dp" android:layout_height="wrap_content" android:layout_toRightOf="@+id/button_inverse" android:layout_alignTop="@+id/button_gray_3" android:text="@string/nored" /> <Button android:id="@+id/button_gray_2" android:layout_width="100dp" android:layout_below="@+id/button_gray_3" android:layout_height="wrap_content" android:text="@string/noblue" /> <Button android:id="@+id/button_flip" android:layout_width="100dp" android:layout_height="wrap_content" android:layout_below="@+id/button_inverse" android:layout_toRightOf="@+id/button_gray_2" android:text="@string/flip" /> <Button android:id="@+id/button_save" android:layout_width="100dp" android:layout_height="wrap_content" android:layout_below="@+id/button_gray_3" android:layout_toRightOf="@+id/button_flip" android:text="@string/save" /> </RelativeLayout> <ImageView android:id="@+id/image_content" android:layout_width="fill_parent" android:layout_height="fill_parent" android:scaleType="fitCenter" android:src="@drawable/ic_launcher" /> </LinearLayout>
MainActivity中的onCreate方法的代码如下：
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView iView = (ImageView) this.findViewById(R.id.image_content);
Bitmap b = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.BLACK);
Canvas c = new Canvas(b);
c.drawText("Load Image from here...", 50, 200, paint);
iView.setImageBitmap(b);
Button saveBtn = (Button) this.findViewById(R.id.button_save);
saveBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
Toast toast = Toast.makeText(getApplicationContext(), "Please load the image firstly...", Toast.LENGTH_SHORT);
toast.show();
loadImage();
ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(srcImage);
if(srcImage != null)
{
//saveFile(srcImage);
}
}
});
Button processBtn = (Button) this.findViewById(R.id.button_gray_3);
processBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
if(srcImage == null)
{
loadImage();
}
ImagePixelsProcessor processor = new ImagePixelsProcessor();
Bitmap bm = processor.gray(srcImage, 2); // 有不同的灰度化策略
final ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(bm);
}
});
Button inverseBtn = (Button) this.findViewById(R.id.button_inverse);
inverseBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
if(srcImage == null)
{
loadImage();
}
ImagePixelsProcessor processor = new ImagePixelsProcessor();
Bitmap bm = processor.brightness(srcImage, 0.3);
final ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(bm);
}
});
Button noRedBtn = (Button) this.findViewById(R.id.button_gray_1);
noRedBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
if(srcImage == null)
{
loadImage();
}
ImagePixelsProcessor processor = new ImagePixelsProcessor();
Bitmap bm = processor.gray(srcImage, 0); // 有不同的灰度化策略
final ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(bm);
}
});
Button gray2Btn = (Button) this.findViewById(R.id.button_gray_2);
gray2Btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
if(srcImage == null)
{
loadImage();
}
ImagePixelsProcessor processor = new ImagePixelsProcessor();
Bitmap bm = processor.gray(srcImage, 1); // 有不同的灰度化策略
final ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(bm);
}
});
Button flipBtn = (Button) this.findViewById(R.id.button_flip);
flipBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View view) {
if(srcImage == null)
{
loadImage();
}
ImagePixelsProcessor processor = new ImagePixelsProcessor();
Bitmap bm = processor.flip(srcImage);
final ImageView iView = (ImageView) findViewById(R.id.image_content);
iView.setImageBitmap(bm);
}
});
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