我内存中有一个位图,我需要将其保存在 bmp 文件中(使用bmp 文件格式 http://en.wikipedia.org/wiki/BMP_file_format).
有什么办法可以在Android上做到这一点吗?
(我读了很多建议使用 png 格式的帖子 - 这是无损的 - 但是,这不是我需要的:我真的需要bmp 格式).
我已经有一些代码可以使用以下命令将其保存为 jpeg 或 png位图压缩 http://developer.android.com/reference/android/graphics/Bitmap.html#compress%28android.graphics.Bitmap.CompressFormat,%20int,%20java.io.OutputStream%29方法 :
/**
* Save data to file using format.
* When format is null : the bitmap will be saved in bmp format
**/
public void writeBitmapToFile(Bitmap data, File file, Bitmap.CompressFormat format) {
FileOutputStream os = null;
try {
os = new FileOutputStream(file);
if(format==null){
//TODO : write data to file using the bmp format
}else{
data.compress(format, 100, os); //ok for JPEG and PNG
}
os.flush();
} catch (Exception e) {
//irrelevant code
} finally {
//irrelevant code
}
}
(我正在回答我自己的问题)
这是我当前的解决方案。它源自此来源:https://github.com/ultrakain/AndroidBitmapUtil https://github.com/ultrakain/AndroidBitmapUtil(感谢 ultrakain 和 @Francescoverheye )
我只是修复了必须添加到每行的虚拟字节计算中的一个小错误(以便每行的长度(以字节为单位)是 4 的倍数(根据 bmp 格式规范的要求)。
我还做了一些改变来提高性能。
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import android.graphics.Bitmap;
import android.util.Log;
public class AndroidBmpUtil {
private static final int BMP_WIDTH_OF_TIMES = 4;
private static final int BYTE_PER_PIXEL = 3;
/**
* Android Bitmap Object to Window's v3 24bit Bmp Format File
* @param orgBitmap
* @param filePath
* @return file saved result
*/
public static boolean save(Bitmap orgBitmap, String filePath) throws IOException {
long start = System.currentTimeMillis();
if(orgBitmap == null){
return false;
}
if(filePath == null){
return false;
}
boolean isSaveSuccess = true;
//image size
int width = orgBitmap.getWidth();
int height = orgBitmap.getHeight();
//image dummy data size
//reason : the amount of bytes per image row must be a multiple of 4 (requirements of bmp format)
byte[] dummyBytesPerRow = null;
boolean hasDummy = false;
int rowWidthInBytes = BYTE_PER_PIXEL * width; //source image width * number of bytes to encode one pixel.
if(rowWidthInBytes%BMP_WIDTH_OF_TIMES>0){
hasDummy=true;
//the number of dummy bytes we need to add on each row
dummyBytesPerRow = new byte[(BMP_WIDTH_OF_TIMES-(rowWidthInBytes%BMP_WIDTH_OF_TIMES))];
//just fill an array with the dummy bytes we need to append at the end of each row
for(int i = 0; i < dummyBytesPerRow.length; i++){
dummyBytesPerRow[i] = (byte)0xFF;
}
}
//an array to receive the pixels from the source image
int[] pixels = new int[width * height];
//the number of bytes used in the file to store raw image data (excluding file headers)
int imageSize = (rowWidthInBytes+(hasDummy?dummyBytesPerRow.length:0)) * height;
//file headers size
int imageDataOffset = 0x36;
//final size of the file
int fileSize = imageSize + imageDataOffset;
//Android Bitmap Image Data
orgBitmap.getPixels(pixels, 0, width, 0, 0, width, height);
//ByteArrayOutputStream baos = new ByteArrayOutputStream(fileSize);
ByteBuffer buffer = ByteBuffer.allocate(fileSize);
/**
* BITMAP FILE HEADER Write Start
**/
buffer.put((byte)0x42);
buffer.put((byte)0x4D);
//size
buffer.put(writeInt(fileSize));
//reserved
buffer.put(writeShort((short)0));
buffer.put(writeShort((short)0));
//image data start offset
buffer.put(writeInt(imageDataOffset));
/** BITMAP FILE HEADER Write End */
//*******************************************
/** BITMAP INFO HEADER Write Start */
//size
buffer.put(writeInt(0x28));
//width, height
//if we add 3 dummy bytes per row : it means we add a pixel (and the image width is modified.
buffer.put(writeInt(width+(hasDummy?(dummyBytesPerRow.length==3?1:0):0)));
buffer.put(writeInt(height));
//planes
buffer.put(writeShort((short)1));
//bit count
buffer.put(writeShort((short)24));
//bit compression
buffer.put(writeInt(0));
//image data size
buffer.put(writeInt(imageSize));
//horizontal resolution in pixels per meter
buffer.put(writeInt(0));
//vertical resolution in pixels per meter (unreliable)
buffer.put(writeInt(0));
buffer.put(writeInt(0));
buffer.put(writeInt(0));
/** BITMAP INFO HEADER Write End */
int row = height;
int col = width;
int startPosition = (row - 1) * col;
int endPosition = row * col;
while( row > 0 ){
for(int i = startPosition; i < endPosition; i++ ){
buffer.put((byte)(pixels[i] & 0x000000FF));
buffer.put((byte)((pixels[i] & 0x0000FF00) >> 8));
buffer.put((byte)((pixels[i] & 0x00FF0000) >> 16));
}
if(hasDummy){
buffer.put(dummyBytesPerRow);
}
row--;
endPosition = startPosition;
startPosition = startPosition - col;
}
FileOutputStream fos = new FileOutputStream(filePath);
fos.write(buffer.array());
fos.close();
Log.v("AndroidBmpUtil" ,System.currentTimeMillis()-start+" ms");
return isSaveSuccess;
}
/**
* Write integer to little-endian
* @param value
* @return
* @throws IOException
*/
private static byte[] writeInt(int value) throws IOException {
byte[] b = new byte[4];
b[0] = (byte)(value & 0x000000FF);
b[1] = (byte)((value & 0x0000FF00) >> 8);
b[2] = (byte)((value & 0x00FF0000) >> 16);
b[3] = (byte)((value & 0xFF000000) >> 24);
return b;
}
/**
* Write short to little-endian byte array
* @param value
* @return
* @throws IOException
*/
private static byte[] writeShort(short value) throws IOException {
byte[] b = new byte[2];
b[0] = (byte)(value & 0x00FF);
b[1] = (byte)((value & 0xFF00) >> 8);
return b;
}
}
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