如何在不改变位图大小的情况下压缩位图？

我使用这种方法来压缩图像

if(bitmapObject.compress(Bitmap.CompressFormat.PNG, 100, fOut))
{
...
}

但是我得到的图像要小得多(在维度上) ，那是在压缩作用之前。

我的应用程序需要发送压缩图像通过网络-所以我想发送尽可能少的数据，因为我可以... 但我必须保持原始大小的图像。

是否有其他方法来保持原始的位图维度与一些压缩？

217234 次浏览
小开
最佳答案

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());

给予

12-07 17:43:36.333: E/Original   dimensions(278): 1024 768
12-07 17:43:36.333: E/Compressed dimensions(278): 1024 768

也许你从一个资源得到你的位图，在这种情况下，位图的维度将取决于手机屏幕的密度

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
小开

如果您使用 PNG 格式，那么它将不会压缩您的图像，因为 PNG 是一种无损格式。使用 JPEG 压缩您的图像，并使用0而不是100的质量。

质素接受程度0-100

0 = MAX 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)

小开

我认为你用这个方法来压缩位图

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);
小开

我是这样做的:

从单体课上获取 压缩位图:

ImageView imageView = (ImageView)findViewById(R.id.imageView);
Bitmap bitmap = ImageUtils.getInstant().getCompressedBitmap("Your_Image_Path_Here");
imageView.setImageBitmap(bitmap);

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;
}
}

压缩 Bitmap 后尺寸相同。

我怎么知道的？

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());

产出:

Before Compress : Dimension: 1080-1452
After Compress : Dimension: 1080-1452

希望这个能帮到你。

小开

这里有一个简短的方法，我用来减少图像的大小有一个高 byteCount(基本上像素)

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)
}

这将返回一个缩放后的 Bitmap，它比作为参数传递的 Bitmap小10倍以上。可能不是最理想的解决方案，但它的工作。

小开

你可以压缩成 webp 来获得最小的尺寸。 首先压缩到 webp，然后压缩到 byteArray。在转换成 byteArray 之后，您可以像下面给出的那样转换成位图

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;
}

这一切都没有失去图像维度。

任何问题请在下面评论


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