[英]converting Java bitmap to byte array
Bitmap bmp = intent.getExtras().get("data");
int size = bmp.getRowBytes() * bmp.getHeight();
ByteBuffer b = ByteBuffer.allocate(size);
bmp.copyPixelsToBuffer(b);
byte[] bytes = new byte[size];
try {
b.get(bytes, 0, bytes.length);
} catch (BufferUnderflowException e) {
// always happens
}
// do something with byte[]
当我在调用copyPixelsToBuffer
之后查看缓冲区时,字节都是 0...从相机返回的位图是不可变的...但这应该无关紧要,因为它正在执行复制。
这段代码可能有什么问题?
尝试这样的事情:
Bitmap bmp = intent.getExtras().get("data");
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();
bmp.recycle();
CompressFormat 太慢了...
试试字节缓冲区。
※※※位图转字节※※※
width = bitmap.getWidth();
height = bitmap.getHeight();
int size = bitmap.getRowBytes() * bitmap.getHeight();
ByteBuffer byteBuffer = ByteBuffer.allocate(size);
bitmap.copyPixelsToBuffer(byteBuffer);
byteArray = byteBuffer.array();
※※※字节转位图※※※
Bitmap.Config configBmp = Bitmap.Config.valueOf(bitmap.getConfig().name());
Bitmap bitmap_tmp = Bitmap.createBitmap(width, height, configBmp);
ByteBuffer buffer = ByteBuffer.wrap(byteArray);
bitmap_tmp.copyPixelsFromBuffer(buffer);
这是用 Kotlin 编写的位图扩展名.convertToByteArray
。
/**
* Convert bitmap to byte array using ByteBuffer.
*/
fun Bitmap.convertToByteArray(): ByteArray {
//minimum number of bytes that can be used to store this bitmap's pixels
val size = this.byteCount
//allocate new instances which will hold bitmap
val buffer = ByteBuffer.allocate(size)
val bytes = ByteArray(size)
//copy the bitmap's pixels into the specified buffer
this.copyPixelsToBuffer(buffer)
//rewinds buffer (buffer position is set to zero and the mark is discarded)
buffer.rewind()
//transfer bytes from buffer into the given destination array
buffer.get(bytes)
//return bitmap's pixels
return bytes
}
也许您需要倒带缓冲区?
此外,如果位图的步幅(以字节为单位)大于以像素为单位的行长度 * 字节/像素,则可能会发生这种情况。 使字节长度为 b.remaining() 而不是大小。
使用以下函数将位图编码为 byte[],反之亦然
public static String encodeTobase64(Bitmap image) {
Bitmap immagex = image;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
immagex.compress(Bitmap.CompressFormat.PNG, 90, baos);
byte[] b = baos.toByteArray();
String imageEncoded = Base64.encodeToString(b, Base64.DEFAULT);
return imageEncoded;
}
public static Bitmap decodeBase64(String input) {
byte[] decodedByte = Base64.decode(input, 0);
return BitmapFactory.decodeByteArray(decodedByte, 0, decodedByte.length);
}
你的字节数组太小了。 每个像素占用 4 个字节,而不仅仅是 1 个,因此将您的大小乘以 * 4,以便数组足够大。
Ted Hopp 是正确的,来自 API 文档:
public void copyPixelsToBuffer (Buffer dst)
“……这个方法返回后,缓冲区的当前位置被更新:位置增加了写入缓冲区的元素数量。”
和
public ByteBuffer get (byte[] dst, int dstOffset, int byteCount)
“从当前位置读取字节到指定的字节数组,从指定的偏移量开始,并按读取的字节数增加位置。”
为了避免较大文件的OutOfMemory
错误,我将通过将位图拆分为几个部分并合并它们部分的字节来解决该任务。
private byte[] getBitmapBytes(Bitmap bitmap)
{
int chunkNumbers = 10;
int bitmapSize = bitmap.getRowBytes() * bitmap.getHeight();
byte[] imageBytes = new byte[bitmapSize];
int rows, cols;
int chunkHeight, chunkWidth;
rows = cols = (int) Math.sqrt(chunkNumbers);
chunkHeight = bitmap.getHeight() / rows;
chunkWidth = bitmap.getWidth() / cols;
int yCoord = 0;
int bitmapsSizes = 0;
for (int x = 0; x < rows; x++)
{
int xCoord = 0;
for (int y = 0; y < cols; y++)
{
Bitmap bitmapChunk = Bitmap.createBitmap(bitmap, xCoord, yCoord, chunkWidth, chunkHeight);
byte[] bitmapArray = getBytesFromBitmapChunk(bitmapChunk);
System.arraycopy(bitmapArray, 0, imageBytes, bitmapsSizes, bitmapArray.length);
bitmapsSizes = bitmapsSizes + bitmapArray.length;
xCoord += chunkWidth;
bitmapChunk.recycle();
bitmapChunk = null;
}
yCoord += chunkHeight;
}
return imageBytes;
}
private byte[] getBytesFromBitmapChunk(Bitmap bitmap)
{
int bitmapSize = bitmap.getRowBytes() * bitmap.getHeight();
ByteBuffer byteBuffer = ByteBuffer.allocate(bitmapSize);
bitmap.copyPixelsToBuffer(byteBuffer);
byteBuffer.rewind();
return byteBuffer.array();
}
试试这个来转换 String-Bitmap 或 Bitmap-String
/**
* @param bitmap
* @return converting bitmap and return a string
*/
public static String BitMapToString(Bitmap bitmap){
ByteArrayOutputStream baos=new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG,100, baos);
byte [] b=baos.toByteArray();
String temp=Base64.encodeToString(b, Base64.DEFAULT);
return temp;
}
/**
* @param encodedString
* @return bitmap (from given string)
*/
public static Bitmap StringToBitMap(String encodedString){
try{
byte [] encodeByte=Base64.decode(encodedString,Base64.DEFAULT);
Bitmap bitmap= BitmapFactory.decodeByteArray(encodeByte, 0, encodeByte.length);
return bitmap;
}catch(Exception e){
e.getMessage();
return null;
}
}
我认为这会做 -
public static byte[] convertBitmapToByteArray(Bitmap bitmap){
ByteBuffer byteBuffer = ByteBuffer.allocate(bitmap.getByteCount());
bitmap.copyPixelsToBuffer(byteBuffer);
byteBuffer.rewind();
return byteBuffer.array();
}
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