我用这个方法压缩一张图片
if(bitmapObject.compress(Bitmap.CompressFormat.PNG, 100, fOut))
{
...
}
但我得到的图像比压缩操作之前小得多（在维度上）。
我的应用程序需要通过网络发送压缩图像 - 所以我想发送尽可能少的数据......但我必须保持图像的原始大小。
还有其他方法可以通过一些压缩来保持原始位图尺寸吗？
【问题讨论】：
标签： android
你确定它更小吗？
Bitmap original = BitmapFactory.decodeStream(getAssets().open("1024x768.jpg"));
ByteArrayOutputStream out = new ByteArrayOutputStream();
original.compress(Bitmap.CompressFormat.PNG, 100, out);
Bitmap decoded = BitmapFactory.decodeStream(new ByteArrayInputStream(out.toByteArray()));
Log.e("Original dimensions", original.getWidth()+" "+original.getHeight());
Log.e("Compressed dimensions", decoded.getWidth()+" "+decoded.getHeight());
给
12-07 17:43:36.333: E/Original dimensions(278): 1024 768
12-07 17:43:36.333: E/Compressed dimensions(278): 1024 768
也许您从资源中获取位图，在这种情况下，位图尺寸将取决于手机屏幕密度
Bitmap bitmap=((BitmapDrawable)getResources().getDrawable(R.drawable.img_1024x768)).getBitmap();
Log.e("Dimensions", bitmap.getWidth()+" "+bitmap.getHeight());
12-07 17:43:38.733: E/Dimensions(278): 768 576
【讨论】：
original.compress(Bitmap.CompressFormat.PNG, 100, out); 值 100 被忽略，因为格式是 png，也许这就是压缩位图返回与原始位图相同尺寸的原因
如果您使用的是 PNG 格式，那么它不会压缩您的图像，因为 PNG 是一种无损格式。使用 JPEG 压缩图像并使用 0 而不是 100 质量。
质量接受 0 - 100
0 = 最大压缩（适用于小图像的最低质量）
100 = 最小压缩（适用于大图像的 MAX 质量）
【讨论】：
我是这样做的：
从单例类中获取压缩位图：
ImageView imageView = (ImageView)findViewById(R.id.imageView);
Bitmap bitmap = ImageUtils.getInstant().getCompressedBitmap("Your_Image_Path_Here");
imageView.setImageBitmap(bitmap);
ImageUtils.java：
public class ImageUtils {
public static ImageUtils mInstant;
public static ImageUtils getInstant(){
if(mInstant==null){
mInstant = new ImageUtils();
}
return mInstant;
}
public Bitmap getCompressedBitmap(String imagePath) {
float maxHeight = 1920.0f;
float maxWidth = 1080.0f;
Bitmap scaledBitmap = null;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
Bitmap bmp = BitmapFactory.decodeFile(imagePath, options);
int actualHeight = options.outHeight;
int actualWidth = options.outWidth;
float imgRatio = (float) actualWidth / (float) actualHeight;
float maxRatio = maxWidth / maxHeight;
if (actualHeight > maxHeight || actualWidth > maxWidth) {
if (imgRatio < maxRatio) {
imgRatio = maxHeight / actualHeight;
actualWidth = (int) (imgRatio * actualWidth);
actualHeight = (int) maxHeight;
} else if (imgRatio > maxRatio) {
imgRatio = maxWidth / actualWidth;
actualHeight = (int) (imgRatio * actualHeight);
actualWidth = (int) maxWidth;
} else {
actualHeight = (int) maxHeight;
actualWidth = (int) maxWidth;
}
}
options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);
options.inJustDecodeBounds = false;
options.inDither = false;
options.inPurgeable = true;
options.inInputShareable = true;
options.inTempStorage = new byte[16 * 1024];
try {
bmp = BitmapFactory.decodeFile(imagePath, options);
} catch (OutOfMemoryError exception) {
exception.printStackTrace();
}
try {
scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888);
} catch (OutOfMemoryError exception) {
exception.printStackTrace();
}
float ratioX = actualWidth / (float) options.outWidth;
float ratioY = actualHeight / (float) options.outHeight;
float middleX = actualWidth / 2.0f;
float middleY = actualHeight / 2.0f;
Matrix scaleMatrix = new Matrix();
scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);
Canvas canvas = new Canvas(scaledBitmap);
canvas.setMatrix(scaleMatrix);
canvas.drawBitmap(bmp, middleX - bmp.getWidth() / 2, middleY - bmp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));
ExifInterface exif = null;
try {
exif = new ExifInterface(imagePath);
int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
Matrix matrix = new Matrix();
if (orientation == 6) {
matrix.postRotate(90);
} else if (orientation == 3) {
matrix.postRotate(180);
} else if (orientation == 8) {
matrix.postRotate(270);
}
scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
} catch (IOException e) {
e.printStackTrace();
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 85, out);
byte[] byteArray = out.toByteArray();
Bitmap updatedBitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
return updatedBitmap;
}
private int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int heightRatio = Math.round((float) height / (float) reqHeight);
final int widthRatio = Math.round((float) width / (float) reqWidth);
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}
final float totalPixels = width * height;
final float totalReqPixelsCap = reqWidth * reqHeight * 2;
while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
inSampleSize++;
}
return inSampleSize;
}
}
位图压缩后尺寸不变。
我是如何检查的？
Bitmap beforeBitmap = BitmapFactory.decodeFile("Your_Image_Path_Here");
Log.i("Before Compress Dimension", beforeBitmap.getWidth()+"-"+beforeBitmap.getHeight());
Bitmap afterBitmap = ImageUtils.getInstant().getCompressedBitmap("Your_Image_Path_Here");
Log.i("After Compress Dimension", afterBitmap.getWidth() + "-" + afterBitmap.getHeight());
输出：
Before Compress : Dimension: 1080-1452
After Compress : Dimension: 1080-1452
希望这会对你有所帮助。
【讨论】：
这是我用来减小具有高byteCount（基本上是像素）的图像大小的一种简短方法
fun resizeImage(image: Bitmap): Bitmap {
val width = image.width
val height = image.height
val scaleWidth = width / 10
val scaleHeight = height / 10
if (image.byteCount <= 1000000)
return image
return Bitmap.createScaledBitmap(image, scaleWidth, scaleHeight, false)
}
这将返回一个比作为参数传递的Bitmap 小10 倍以上的缩放位图。可能不是最理想的解决方案，但它确实有效。
【讨论】：
您可以压缩成 webp 以获得最小的大小。 所以先压缩成webp再压缩成byteArray。转换为 byteArray 后，您可以转换为如下所示的位图
public Bitmap compress(Bitmap yourBitmap){
//converted into webp into lowest quality
ByteArrayOutputStream stream = new ByteArrayOutputStream();
yourBitmap.compress(Bitmap.CompressFormat.WEBP,0,stream);//0=lowest, 100=highest quality
byte[] byteArray = stream.toByteArray();
//convert your byteArray into bitmap
Bitmap yourCompressBitmap = BitmapFactory.decodeByteArray(byteArray,0,byteArray.length);
return yourCompressBitmap;
}
这一切都在不丢失图像尺寸的情况下完成。
有什么问题请在下方留言
【讨论】：
我认为你使用这种方法来压缩位图
BitmapFactory.Option imageOpts = new BitmapFactory.Options ();
imageOpts.inSampleSize = 2; // for 1/2 the image to be loaded
Bitmap thumb = Bitmap.createScaledBitmap (BitmapFactory.decodeFile(photoPath, imageOpts), 96, 96, false);
【讨论】：