如何在上载到服务器之前减less图像文件大小

许多应用程序允许共享图像，这是从画廊挑选。

他们上传的原始图像文件？ 这就像1-3 MB？ 或者他们处理？

在任何情况下，我怎样才能从文件path中获取图像，通过降低分辨率来减小图像大小，并将其保存在其他位置并尝试上传？

我试过了：

Bitmap photo = decodeSampledBitmapFromFile(filePath, DESIRED_WIDTH, DESIRED_HEIGHT); FileOutputStream out = new FileOutputStream(filePath); photo.compress(Bitmap.CompressFormat.JPEG, 100, out); public static Bitmap decodeSampledBitmapFromFile(String path, int reqWidth, int reqHeight) { final BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeFile(path, options); final int height = options.outHeight; final int width = options.outWidth; options.inPreferredConfig = Bitmap.Config.ARGB_8888; int inSampleSize = 1; if (height > reqHeight) { inSampleSize = Math.round((float) height / (float) reqHeight); } int expectedWidth = width / inSampleSize; if (expectedWidth > reqWidth) { inSampleSize = Math.round((float) width / (float) reqWidth); } options.inSampleSize = inSampleSize; options.inJustDecodeBounds = false; return BitmapFactory.decodeFile(path, options); } 

但这是他们正确的做法吗？ 因为我已经看到了答案，提示compression operation takes rather big amount of time 在这里 compression operation takes rather big amount of time

Answer 1

这是很好的尝试这个

 private String decodeFile(String path,int DESIREDWIDTH, int DESIREDHEIGHT) { String strMyImagePath = null; Bitmap scaledBitmap = null; try { // Part 1: Decode image Bitmap unscaledBitmap = ScalingUtilities.decodeFile(path, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT); if (!(unscaledBitmap.getWidth() <= DESIREDWIDTH && unscaledBitmap.getHeight() <= DESIREDHEIGHT)) { // Part 2: Scale image scaledBitmap = ScalingUtilities.createScaledBitmap(unscaledBitmap, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT); } else { unscaledBitmap.recycle(); return path; } // Store to tmp file String extr = Environment.getExternalStorageDirectory().toString(); File mFolder = new File(extr + "/TMMFOLDER"); if (!mFolder.exists()) { mFolder.mkdir(); } String s = "tmp.png"; File f = new File(mFolder.getAbsolutePath(), s); strMyImagePath = f.getAbsolutePath(); FileOutputStream fos = null; try { fos = new FileOutputStream(f); scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 75, fos); fos.flush(); fos.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } scaledBitmap.recycle(); } catch (Throwable e) { } if (strMyImagePath == null) { return path; } return strMyImagePath; } 

ScalingUtilities.java

 import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; import android.graphics.BitmapFactory; import android.graphics.BitmapFactory.Options; import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Rect; /** * Class containing static utility methods for bitmap decoding and scaling * * @author */ public class ScalingUtilities { /** * Utility function for decoding an image resource. The decoded bitmap will * be optimized for further scaling to the requested destination dimensions * and scaling logic. * * @param res The resources object containing the image data * @param resId The resource id of the image data * @param dstWidth Width of destination area * @param dstHeight Height of destination area * @param scalingLogic Logic to use to avoid image stretching * @return Decoded bitmap */ public static Bitmap decodeResource(Resources res, int resId, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { Options options = new Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeResource(res, resId, options); options.inJustDecodeBounds = false; options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth, dstHeight, scalingLogic); Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId, options); return unscaledBitmap; } public static Bitmap decodeFile(String path, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { Options options = new Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeFile(path, options); options.inJustDecodeBounds = false; options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth, dstHeight, scalingLogic); Bitmap unscaledBitmap = BitmapFactory.decodeFile(path, options); return unscaledBitmap; } /** * Utility function for creating a scaled version of an existing bitmap * * @param unscaledBitmap Bitmap to scale * @param dstWidth Wanted width of destination bitmap * @param dstHeight Wanted height of destination bitmap * @param scalingLogic Logic to use to avoid image stretching * @return New scaled bitmap object */ public static Bitmap createScaledBitmap(Bitmap unscaledBitmap, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic); Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic); Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(), Config.ARGB_8888); Canvas canvas = new Canvas(scaledBitmap); canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG)); return scaledBitmap; } /** * ScalingLogic defines how scaling should be carried out if source and * destination image has different aspect ratio. * * CROP: Scales the image the minimum amount while making sure that at least * one of the two dimensions fit inside the requested destination area. * Parts of the source image will be cropped to realize this. * * FIT: Scales the image the minimum amount while making sure both * dimensions fit inside the requested destination area. The resulting * destination dimensions might be adjusted to a smaller size than * requested. */ public static enum ScalingLogic { CROP, FIT } /** * Calculate optimal down-sampling factor given the dimensions of a source * image, the dimensions of a destination area and a scaling logic. * * @param srcWidth Width of source image * @param srcHeight Height of source image * @param dstWidth Width of destination area * @param dstHeight Height of destination area * @param scalingLogic Logic to use to avoid image stretching * @return Optimal down scaling sample size for decoding */ public static int calculateSampleSize(int srcWidth, int srcHeight, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { if (scalingLogic == ScalingLogic.FIT) { final float srcAspect = (float)srcWidth / (float)srcHeight; final float dstAspect = (float)dstWidth / (float)dstHeight; if (srcAspect > dstAspect) { return srcWidth / dstWidth; } else { return srcHeight / dstHeight; } } else { final float srcAspect = (float)srcWidth / (float)srcHeight; final float dstAspect = (float)dstWidth / (float)dstHeight; if (srcAspect > dstAspect) { return srcHeight / dstHeight; } else { return srcWidth / dstWidth; } } } /** * Calculates source rectangle for scaling bitmap * * @param srcWidth Width of source image * @param srcHeight Height of source image * @param dstWidth Width of destination area * @param dstHeight Height of destination area * @param scalingLogic Logic to use to avoid image stretching * @return Optimal source rectangle */ public static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { if (scalingLogic == ScalingLogic.CROP) { final float srcAspect = (float)srcWidth / (float)srcHeight; final float dstAspect = (float)dstWidth / (float)dstHeight; if (srcAspect > dstAspect) { final int srcRectWidth = (int)(srcHeight * dstAspect); final int srcRectLeft = (srcWidth - srcRectWidth) / 2; return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight); } else { final int srcRectHeight = (int)(srcWidth / dstAspect); final int scrRectTop = (int)(srcHeight - srcRectHeight) / 2; return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight); } } else { return new Rect(0, 0, srcWidth, srcHeight); } } /** * Calculates destination rectangle for scaling bitmap * * @param srcWidth Width of source image * @param srcHeight Height of source image * @param dstWidth Width of destination area * @param dstHeight Height of destination area * @param scalingLogic Logic to use to avoid image stretching * @return Optimal destination rectangle */ public static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, ScalingLogic scalingLogic) { if (scalingLogic == ScalingLogic.FIT) { final float srcAspect = (float)srcWidth / (float)srcHeight; final float dstAspect = (float)dstWidth / (float)dstHeight; if (srcAspect > dstAspect) { return new Rect(0, 0, dstWidth, (int)(dstWidth / srcAspect)); } else { return new Rect(0, 0, (int)(dstHeight * srcAspect), dstHeight); } } else { return new Rect(0, 0, dstWidth, dstHeight); } } } 

Answer 2

我使用这个函数在上传之前缩小图像的大小，将图像大小缩小到接近200 KB，并保持质量相对良好，您可以通过更改REQUIRED_SIZE和inSampleSize来修改它以达到您的目的：

 public File saveBitmapToFile(File file){ try { // BitmapFactory options to downsize the image BitmapFactory.Options o = new BitmapFactory.Options(); o.inJustDecodeBounds = true; o.inSampleSize = 6; // factor of downsizing the image FileInputStream inputStream = new FileInputStream(file); //Bitmap selectedBitmap = null; BitmapFactory.decodeStream(inputStream, null, o); inputStream.close(); // The new size we want to scale to final int REQUIRED_SIZE=75; // Find the correct scale value. It should be the power of 2. int scale = 1; while(o.outWidth / scale / 2 >= REQUIRED_SIZE && o.outHeight / scale / 2 >= REQUIRED_SIZE) { scale *= 2; } BitmapFactory.Options o2 = new BitmapFactory.Options(); o2.inSampleSize = scale; inputStream = new FileInputStream(file); Bitmap selectedBitmap = BitmapFactory.decodeStream(inputStream, null, o2); inputStream.close(); // here i override the original image file file.createNewFile(); FileOutputStream outputStream = new FileOutputStream(file); selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 100 , outputStream); return file; } catch (Exception e) { return null; } } 

注：我调整和覆盖这个function的原始文件图像，你也可以写到另一个文件。

我希望它可以帮助你。

Answer 3

使用此方法返回压缩到200 KB左右的位图图像。 你可以configuration它得到一个你想要的任何大小的位图图像。

 public static Bitmap scaleImage(Context context, Uri photoUri) throws IOException { InputStream is = context.getContentResolver().openInputStream(photoUri); BitmapFactory.Options dbo = new BitmapFactory.Options(); dbo.inJustDecodeBounds = true; BitmapFactory.decodeStream(is, null, dbo); is.close(); int rotatedWidth, rotatedHeight; int orientation = getOrientation(context, photoUri); if (orientation == 90 || orientation == 270) { rotatedWidth = dbo.outHeight; rotatedHeight = dbo.outWidth; } else { rotatedWidth = dbo.outWidth; rotatedHeight = dbo.outHeight; } Bitmap srcBitmap; is = context.getContentResolver().openInputStream(photoUri); if (rotatedWidth > MAX_IMAGE_DIMENSION || rotatedHeight > MAX_IMAGE_DIMENSION) { float widthRatio = ((float) rotatedWidth) / ((float) MAX_IMAGE_DIMENSION); float heightRatio = ((float) rotatedHeight) / ((float) MAX_IMAGE_DIMENSION); float maxRatio = Math.max(widthRatio, heightRatio); // Create the bitmap from file BitmapFactory.Options options = new BitmapFactory.Options(); options.inSampleSize = (int) maxRatio; srcBitmap = BitmapFactory.decodeStream(is, null, options); } else { srcBitmap = BitmapFactory.decodeStream(is); } is.close(); /* * if the orientation is not 0 (or -1, which means we don't know), we * have to do a rotation. */ if (orientation > 0) { Matrix matrix = new Matrix(); matrix.postRotate(orientation); srcBitmap = Bitmap.createBitmap(srcBitmap, 0, 0, srcBitmap.getWidth(), srcBitmap.getHeight(), matrix, true); } String type = context.getContentResolver().getType(photoUri); ByteArrayOutputStream baos = new ByteArrayOutputStream(); if (type.equals("image/png")) { srcBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos); } else if (type.equals("image/jpg") || type.equals("image/jpeg")) { srcBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos); } byte[] bMapArray = baos.toByteArray(); baos.close(); return BitmapFactory.decodeByteArray(bMapArray, 0, bMapArray.length); } 

Answer 4

这是我的解决scheme

 public static boolean reduceImage(String path, long maxSize) { File img = new File(path); boolean result = false; BitmapFactory.Options options = new BitmapFactory.Options(); Bitmap bitmap = null; options.inSampleSize=1; while (img.length()>maxSize) { img = new File(path); options.inSampleSize = options.inSampleSize+1; bitmap = BitmapFactory.decodeFile(path, options); Utils.deleteRecursive(path); result = saveImage(bitmap, path); }; return result; }