Android如何创建运行时缩略图

Question

我有一个大尺寸的图像。在运行时，我想从存储器中读取图像，并对其进行缩放，以减少其重量和大小，并将其用作缩略图。当用户单击缩略图时，我想显示全尺寸的图像。

Answer 1

我找到的最佳解决方案如下。与其他解决方案相比，此解决方案不需要加载完整图像来创建缩略图，因此效率更高！它的限制是，你不能有一个精确的宽度和高度缩略图，但解决方案尽可能接近。

File file = ...; // the image file

Options bitmapOptions = new Options();
bitmapOptions.inJustDecodeBounds = true; // obtain the size of the image, without loading it in memory
BitmapFactory.decodeFile(file.getAbsolutePath(), bitmapOptions);

// find the best scaling factor for the desired dimensions
int desiredWidth = 400;
int desiredHeight = 300;
float widthScale = (float)bitmapOptions.outWidth/desiredWidth;
float heightScale = (float)bitmapOptions.outHeight/desiredHeight;
float scale = Math.min(widthScale, heightScale);

int sampleSize = 1;
while (sampleSize < scale) {
    sampleSize *= 2;
}
bitmapOptions.inSampleSize = sampleSize; // this value must be a power of 2,
                                         // this is why you can not have an image scaled as you would like
bitmapOptions.inJustDecodeBounds = false; // now we want to load the image

// Let's load just the part of the image necessary for creating the thumbnail, not the whole image
Bitmap thumbnail = BitmapFactory.decodeFile(file.getAbsolutePath(), bitmapOptions);

// Save the thumbnail
File thumbnailFile = ...;
FileOutputStream fos = new FileOutputStream(thumbnailFile);
thumbnail.compress(Bitmap.CompressFormat.JPEG, 90, fos);
fos.flush();
fos.close();

// Use the thumbail on an ImageView or recycle it!
thumbnail.recycle();

Answer 2

我的解决方案

byte[] imageData = null;

        try     
        {

            final int THUMBNAIL_SIZE = 64;

            FileInputStream fis = new FileInputStream(fileName);
            Bitmap imageBitmap = BitmapFactory.decodeStream(fis);

            imageBitmap = Bitmap.createScaledBitmap(imageBitmap, THUMBNAIL_SIZE, THUMBNAIL_SIZE, false);

            ByteArrayOutputStream baos = new ByteArrayOutputStream();  
            imageBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
            imageData = baos.toByteArray();

        }
        catch(Exception ex) {

        }

Answer 3

试试这个

Bitmap ThumbImage = ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(imagePath), THUMBSIZE, THUMBSIZE);

此实用程序可从API_LEVEl 8获得。[来源]