Android开发中经常有如下需求：
1.由file decode bitmap
如果硬盘中的图片文件过大，不进行压缩，直接decode到内存，会有内存溢出的风险。
可利用BitmapFactory.Options设置inSampleSize（采样率）即可。
计算采样率，通常缩小图片的宽或者高（减少像素点，图片内容完整，如果减少得过分了，图片文件会模糊）为原来的1/2、1/4、1/8，就是缩放2的倍数。
/*
* 由file转bitmap
*/
public static Bitmap decodeBitmapFromFilePath(String path, int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;//如此，无法decode bitmap
BitmapFactory.decodeFile(path, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;//如此，方可decode bitmap
return BitmapFactory.decodeFile(path, options);
}
/*
* 计算采样率
*/
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}使用示例：
BitmapUtils.decodeBitmapFromFilePath("图片路径", 800,800);2.拍照或者相册选择图片后压缩上传服务器（比如3M图片压缩到50-200KB）
拍照或者相册选择图片后，能得到一个图片的路径，首先需要根据图片路径，利用采样率压缩一次，
如BitmapUtils.decodeBitmapFromFilePath(“图片路径”, 800,800);
如此操作得到的bitmap再压缩为字节输出流，然后写入file,就可以上传服务器了（当然，上传图片到服务器有多种方式）。
bitmap再压缩为字节输出流(可以判断字节流大小，再决定是否继续压缩)再写入file，是耗时操作，必须放到子线程中执行。
如下所示：
private String pathSource;//原图文件路径
private String pathCompressed;//压缩后的图片文件路径
private int kb_max = 1000;//压缩到多少KB，不能精确，只能<=kb_max
private int quality_max = 80;//压缩精度，尽量>=50
private int reqWidth = 1000;//期望的图片宽度
private int reqHeight = 1000;//期望的图片高度final Bitmap bitmap = decodeBitmapFromFilePath(compressFileBean.getPathSource(), compressFileBean.getReqWidth(), compressFileBean.getReqHeight());
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
int quality = 80;
//压缩格式选取JPEG就行了，quality，压缩精度尽量不要低于50，否则影响清晰度
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, byteArrayOutputStream);
while (byteArrayOutputStream.toByteArray().length / 1024 > compressFileBean.getKb_max() && quality > compressFileBean.getQuality_max()) {
// 循环判断如果压缩后图片是否大于kb_max kb,大于继续压缩,
byteArrayOutputStream.reset();
quality -= 10;
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, byteArrayOutputStream);
}
try {
final File fileCompressed = createFile(compressFileBean.getPathCompressed());
FileOutputStream fileOutputStream = new FileOutputStream(fileCompressed);
fileOutputStream.write(byteArrayOutputStream.toByteArray());//写入目标文件
fileOutputStream.flush();
fileOutputStream.close();
byteArrayOutputStream.close();
if (fileCompressed != null && fileCompressed.length() > 0)
runOnUiThread(new Runnable() {
@Override
public void run() {
//压缩成功
compressFileCallback.onCompressFileFinished(fileCompressed, bitmap);
}
});
} catch (final Exception e) {
e.printStackTrace();
runOnUiThread(new Runnable() {
@Override
public void run() {
//压缩失败
compressFileCallback.onCompressFileFailed("压缩图片文件失败" + e.getMessage());
}
});
}使用示例：
BitmapUtils.compressFile(new BitmapUtils.CompressFileBean.Builder()
.setFileSource(file.getAbsolutePath())
.setFileCompressed(getExternalCacheDir() + File.separator + "Feedback" + File.separator + System.currentTimeMillis() + ".jpg")
.setKb_max(100)
.setQuality_max(50)
.setReqWidth(800)
.setReqHeight(800).build(), new BitmapUtils.CompressFileCallback() {
@Override
public void onCompressFileFinished(File file, Bitmap bitmap) {
// if (feedbackUI.getRvAdapter().getList_bean().size() == 3)
// feedbackUI.getRvAdapter().setHaveFootView(false);
// feedbackUI.getRvAdapter().add(file);
}
@Override
public void onCompressFileFailed(String s) {
}
});小编封装了一个常用的BitmapUtils:
public class BitmapUtils {
/*
* 计算采样率
*/
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}
/**
* 裁剪
*
* @param bitmap 原图
* @return 裁剪后的图像
*/
public static Bitmap cropBitmap(Bitmap bitmap, float hRatioW) {
int w = bitmap.getWidth(); // 得到图片的宽，高
int h = bitmap.getHeight();
return Bitmap.createBitmap(bitmap, 0, 0, w, (int) (w * hRatioW), null, false);
}
/**
* 按比例缩放图片
*
* @param origin 原图
* @param ratio 比例
* @return 新的bitmap
*/
public static Bitmap scaleBitmap(Bitmap origin, float ratio) {
if (origin == null) {
return null;
}
int width = origin.getWidth();
int height = origin.getHeight();
Matrix matrix = new Matrix();
matrix.preScale(ratio, ratio);
Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, false);
return newBM;
}
/*
* 质量压缩法：将图片文件压缩,压缩是耗时操作
*/
public static void compressFile(CompressFileBean compressFileBean, CompressFileCallback compressFileCallback) {
new CompressFileThread(compressFileBean, compressFileCallback).start();
}
/*
* 由file转bitmap
*/
public static Bitmap decodeBitmapFromFilePath(String path, int reqWidth, int reqHeight) {
// First decode with inJustDecodeBounds=true to check dimensions
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;//如此，无法decode bitmap
BitmapFactory.decodeFile(path, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;//如此，方可decode bitmap
return BitmapFactory.decodeFile(path, options);
}
/**
* 根据路径 创建文件
*
* @param pathFile
* @return
* @throws IOException
*/
private static File createFile(String pathFile) throws IOException {
File fileDir = new File(pathFile.substring(0, pathFile.lastIndexOf(File.separator)));
File file = new File(pathFile);
if (!fileDir.exists()) fileDir.mkdirs();
if (!file.exists()) file.createNewFile();
return file;
}
/**
* 读取图片的旋转的角度
*
* @param path 图片绝对路径
* @return 图片的旋转角度
*/
public static int getBitmapDegree(String path) {
int degree = 0;
try {
// 从指定路径下读取图片，并获取其EXIF信息
ExifInterface exifInterface = new ExifInterface(path);
// 获取图片的旋转信息
int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION,
ExifInterface.ORIENTATION_NORMAL);
switch (orientation) {
case ExifInterface.ORIENTATION_ROTATE_90:
degree = 90;
break;
case ExifInterface.ORIENTATION_ROTATE_180:
degree = 180;
break;
case ExifInterface.ORIENTATION_ROTATE_270:
degree = 270;
break;
}
} catch (IOException e) {
e.printStackTrace();
}
return degree;
}
/**
* 将图片按照某个角度进行旋转
*
* @param bm 需要旋转的图片
* @param degree 旋转角度
* @return 旋转后的图片
*/
public static Bitmap rotateBitmapByDegree(Bitmap bm, int degree) {
Bitmap returnBm = null;
// 根据旋转角度，生成旋转矩阵
Matrix matrix = new Matrix();
matrix.postRotate(degree);
try {
// 将原始图片按照旋转矩阵进行旋转，并得到新的图片
returnBm = Bitmap.createBitmap(bm, 0, 0, bm.getWidth(), bm.getHeight(), matrix, true);
} catch (OutOfMemoryError e) {
}
if (returnBm == null) {
returnBm = bm;
}
if (bm != returnBm) {
bm.recycle();
}
return returnBm;
}
/**
* 对View进行量测，布局后截图
*
* @param view
* @return
*/
public static Object[] captureViewToBitmap(View view) {
view.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
int width = view.getMeasuredWidth();
int height = view.getMeasuredHeight();
view.layout(0, 0, width, height);
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444);
Canvas canvas = new Canvas(bitmap);
view.draw(canvas);
Object[] objects = new Object[3];
objects[0] = bitmap;
objects[1] = width;
objects[2] = height;
return objects;
}
/**
* 对View进行量测，布局后截图
*
* @param view
* @return
*/
public static Bitmap captureViewToBitmap(View view, int reqWidth, int reqHeight) {
view.layout(0, 0, reqWidth, reqHeight);
Bitmap bitmap = Bitmap.createBitmap(reqWidth, reqHeight, Bitmap.Config.ARGB_4444);
// CYLogUtils.log("bitmap原始width", bitmap.getWidth());
// CYLogUtils.log("bitmap原始height", bitmap.getHeight());
Canvas canvas = new Canvas(bitmap);
view.draw(canvas);
return bitmap;
}
/*
压缩bitmap,会被压缩到指定宽高
*/
public static Bitmap compressBitmap(Bitmap bitmap, int reqWidth, int reqHeight) {
return Bitmap.createScaledBitmap(bitmap, reqWidth, reqHeight, true);
}
private static class CompressFileThread extends Thread {
private Handler handler_deliver = new Handler(Looper.getMainLooper());
private CompressFileBean compressFileBean;
private CompressFileCallback compressFileCallback;
public CompressFileThread(CompressFileBean compressFileBean, CompressFileCallback compressFileCallback) {
this.compressFileBean = compressFileBean;
this.compressFileCallback = compressFileCallback;
}
@Override
public void run() {
super.run();
final Bitmap bitmap = decodeBitmapFromFilePath(compressFileBean.getPathSource(), compressFileBean.getReqWidth(), compressFileBean.getReqHeight());
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
int quality = 80;
//压缩格式选取JPEG就行了，quality，压缩精度尽量不要低于50，否则影响清晰度
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, byteArrayOutputStream);
while (byteArrayOutputStream.toByteArray().length / 1024 > compressFileBean.getKb_max() && quality > compressFileBean.getQuality_max()) {
// 循环判断如果压缩后图片是否大于kb_max kb,大于继续压缩,
byteArrayOutputStream.reset();
quality -= 10;
bitmap.compress(Bitmap.CompressFormat.JPEG, quality, byteArrayOutputStream);
}
try {
final File fileCompressed = createFile(compressFileBean.getPathCompressed());
FileOutputStream fileOutputStream = new FileOutputStream(fileCompressed);
fileOutputStream.write(byteArrayOutputStream.toByteArray());//写入目标文件
fileOutputStream.flush();
fileOutputStream.close();
byteArrayOutputStream.close();
if (fileCompressed != null && fileCompressed.length() > 0)
runOnUiThread(new Runnable() {
@Override
public void run() {
//压缩成功
compressFileCallback.onCompressFileFinished(fileCompressed, bitmap);
}
});
} catch (final Exception e) {
e.printStackTrace();
runOnUiThread(new Runnable() {
@Override
public void run() {
//压缩失败
compressFileCallback.onCompressFileFailed("压缩图片文件失败" + e.getMessage());
}
});
}
}
private void runOnUiThread(Runnable run) {
handler_deliver.post(run);
}
}
public static class CompressFileBean {
private String pathSource;//原图文件路径
private String pathCompressed;//压缩后的图片文件路径
private int kb_max = 1000;//压缩到多少KB，不能精确，只能<=kb_max
private int quality_max = 80;//压缩精度，尽量>=50
private int reqWidth = 1000;//期望的图片宽度
private int reqHeight = 1000;//期望的图片高度
private CompressFileBean(Builder builder) {
this.pathSource = builder.getFileSource();
this.pathCompressed = builder.getFileCompressed();
this.kb_max = builder.getKb_max();
this.quality_max = builder.getQuality_max();
this.reqWidth = builder.getReqWidth();
this.reqHeight = builder.getReqHeight();
}
public static class Builder {
private String pathSource;//原图文件路径
private String pathCompressed;//压缩后的图片文件路径
private int kb_max = 1000;//压缩到多少KB，不能精确，只能<=kb_max
private int quality_max = 80;//压缩精度，尽量>=50
private int reqWidth = 1000;//期望的图片宽度
private int reqHeight = 1000;//期望的图片高度
public String getFileSource() {
return pathSource;
}
public Builder setFileSource(String pathSource) {
this.pathSource = pathSource;
return this;
}
public String getFileCompressed() {
return pathCompressed;
}
public Builder setFileCompressed(String pathCompressed) {
this.pathCompressed = pathCompressed;
return this;
}
public int getKb_max() {
return kb_max;
}
public Builder setKb_max(int kb_max) {
this.kb_max = kb_max;
return this;
}
public int getQuality_max() {
return quality_max;
}
public Builder setQuality_max(int quality_max) {
this.quality_max = quality_max;
return this;
}
public int getReqWidth() {
return reqWidth;
}
public Builder setReqWidth(int reqWidth) {
this.reqWidth = reqWidth;
return this;
}
public int getReqHeight() {
return reqHeight;
}
public Builder setReqHeight(int reqHeight) {
this.reqHeight = reqHeight;
return this;
}
public CompressFileBean build() {
return new CompressFileBean(this);
}
}
public String getPathSource() {
return pathSource;
}
public String getPathCompressed() {
return pathCompressed;
}
public int getKb_max() {
return kb_max;
}
public int getQuality_max() {
return quality_max;
}
public int getReqWidth() {
return reqWidth;
}
public int getReqHeight() {
return reqHeight;
}
}
public static interface CompressFileCallback {
//图片压缩成功
public void onCompressFileFinished(File file, Bitmap bitmap);
//图片压缩失败
public void onCompressFileFailed(String errorMsg);
}
}
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