最近看到一篇关于图像处理的blog，感觉挺有用的，转载过来收藏下
在开发中，当我们需要的有一张大图片同时还需要一些小图片时，我们只需要通过代码对此图片进行不同比例的缩放即可，这样大大节约资源，减小了安装包的尺寸 。除缩放外，我们还经常对图片进行其他操作如裁剪、旋转、存储等。
这样我们可以编写对于图片进行处理的通用组件，方便开发。下面就分享一下对图片进行处理的组件BitmapUtil，案例界面：
1、 通过 BitmapFactory 取得Bitmap
Bitmap bm=BitmapFactory.decodeStream(InputStream is );
Bitmap newbm = Bitmap.createBitmap( Bitmap s, int x, int y, int w, int h, Matrix m, boolean f);该方法可实现位图的缩放、裁剪、旋转操作
Bitmap s：要处理的原始位图
int x ,y：起始位置坐标
int w：要截的图的宽度
int h：要截的图的宽度
Matrix m 矩阵，主要是用于平面的缩放、平移、旋转
boolean f：是否保证等比
返回值：返回处理后的Bitmap
可实现对图片进行按比例缩放、图片按比例裁剪、圆形图片处理等方法，实现功能如下：
/**
* 通过资源id转化成Bitmap
* @param context
* @param resId
* @return
*/
public static Bitmap readBitmapById(Context context, int resId){
BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inPreferredConfig = Bitmap.Config.RGB_565;
opt.inPurgeable = true;
opt.inInputShareable = true;
InputStream is = context.getResources().openRawResource(resId);
return BitmapFactory.decodeStream(is, null, opt);
}
执行效果如图：
/**
* 缩放图片
* @param bm 要缩放图片
* @param newWidth 宽度
* @param newHeight 高度
* @return处理后的图片
*/
public static Bitmap scaleImage(Bitmap bm, int newWidth, int newHeight){
if (bm == null){
return null;
}
int width = bm.getWidth();
int height = bm.getHeight();
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap newbm = Bitmap.createBitmap(bm, 0, 0, width, height, matrix,true);
if (bm != null & !bm.isRecycled()){
bm.recycle();//销毁原图片
bm = null;
}
return newbm;
}
执行效果如图：
/**
* 按照一定的宽高比例裁剪图片
* @param bitmap 要裁剪的图片
* @param num1 长边的比例
* @param num2 短边的比例
* @param isRecycled是否回收原图片
* @return 裁剪后的图片
*/
public static Bitmap imageCrop(Bitmap bitmap, int num1, int num2, boolean isRecycled){
if (bitmap == null){
return null;
}
int w = bitmap.getWidth(); // 得到图片的宽，高
int h = bitmap.getHeight();
int retX, retY;
int nw, nh;
if (w > h){
if (h > w * num2 / num1){
nw = w;
nh = w * num2 / num1;
retX = 0;
retY = (h - nh) / 2;
} else{
nw = h * num1 / num2;
nh = h;
retX = (w - nw) / 2;
retY = 0;
}
} else{
if (w > h * num2 / num1){
nh = h;
nw = h * num2 / num1;
retY = 0;
retX = (w - nw) / 2;
} else{
nh = w * num1 / num2;
nw = w;
retY = (h - nh) / 2;
retX = 0;}
}
Bitmap bmp = Bitmap.createBitmap(bitmap, retX, retY, nw, nh, null,false);
if (isRecycled && bitmap != null && !bitmap.equals(bmp)&& !bitmap.isRecycled()){
bitmap.recycle();//回收原图片
bitmap = null;
}
return bmp;
}
执行效果如图：
/**
*图片转圆角
* @param bitmap需要转的bitmap
* @param pixels转圆角的弧度
* @return 转圆角的bitmap
*/
public static Bitmap toRoundCorner(Bitmap bitmap, int pixels) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final RectF rectF = new RectF(rect);
final float roundPx = pixels;
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
if (bitmap != null && !bitmap.isRecycled())
{
bitmap.recycle();
}
return output;
}
执行效果如图：
public static Bitmap toRoundBitmap(Bitmap bitmap){
if (bitmap == null){
return null;
}
int width = bitmap.getWidth();
int height = bitmap.getHeight();
float roundPx;
float left, top, right, bottom, dst_left, dst_top, dst_right, dst_bottom;
if (width <= height){
roundPx = width / 2;
top = 0;
bottom = width;
left = 0;
right = width;
height = width;
dst_left = 0;
dst_top = 0;
dst_right = width;
dst_bottom = width;
} else{
roundPx = height / 2;
float clip = (width - height) / 2;
left = clip;
right = width - clip;
top = 0;
bottom = height;
width = height;
dst_left = 0;
dst_top = 0;
dst_right = height;
dst_bottom = height;
}
Bitmap output = Bitmap.createBitmap(width, height, Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect src = new Rect((int) left, (int) top, (int) right,
(int) bottom);
final Rect dst = new Rect((int) dst_left, (int) dst_top,
(int) dst_right, (int) dst_bottom);
final RectF rectF = new RectF(dst);
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, src, dst, paint);
if (bitmap != null && !bitmap.isRecycled()){
bitmap.recycle();
bitmap = null;
}
return output;
}
执行效果如图：
/**
* 旋转图片
* @param angle 旋转角度
* @param bitmap 要处理的Bitmap
* @return 处理后的Bitmap
*/
public static Bitmap rotaingImageView(int angle, Bitmap bitmap)
{
// 旋转图片 动作
Matrix matrix = new Matrix();
matrix.postRotate(angle);
// 创建新的图片
Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0,
bitmap.getWidth(), bitmap.getHeight(), matrix, true);
if (resizedBitmap != bitmap && bitmap != null && !bitmap.isRecycled()){
bitmap.recycle();
bitmap = null;
}
return resizedBitmap;
}
public static boolean saveBmpToSd(String dir, Bitmap bm, String filename,
int quantity, boolean recyle) {
boolean ret = true;
if (bm == null) {
return false;}
File dirPath = new File(dir);
if (!exists(dir)) {
dirPath.mkdirs();
}
if (!dir.endsWith(File.separator)) {
dir += File.separator;
}
File file = new File(dir + filename);
OutputStream outStream = null;
try {
file.createNewFile();
outStream = new FileOutputStream(file);
bm.compress(Bitmap.CompressFormat.JPEG, quantity, outStream);
} catch (Exception e) {
e.printStackTrace();
ret = false;
} finally {
try {
if (outStream != null) outStream.close();
} catch (IOException e) {
e.printStackTrace();
}
if (recyle && !bm.isRecycled()) {
bm.recycle();
bm = null;
}
}
return ret;
}