问题
My metadata is stored in a 8 bit unsigned dataset in a HDF5 file. After importing to DM, it become a 2D image of 1*length dimension. Each "pixel" stores the ASCII value of the corresponding value to the character. For further processing, I have to convert the ASCII array to a single string, and further to TagGroup. Here is the stupid method (pixel by pixel) I currently do:
String Img2Str (image img){
Number dim1, dim2
img.getsize(dim1,dim2)
string out = ""
for (number i=0; i<dim1*dim2; i++)
out += img.getpixel(0,i).chr()
Return out
}
This pixel-wise operation is really quite slow! Is there any other faster method to do this work?
回答1:
Yes, there is a better way. You really want to look into the chapter of raw-data streaming:
If you hold raw data in a "stream" object, you can read and write it in any form you like. So the solution to your problem is to
- Create a stream
- Add the "image" to the stream (writing binary data)
- Reset the steam position to the start
- Read out the binary data a string
This is the code:
{
number sx = 10
number sy = 10
image textImg := IntegerImage( "Text", 1, 0 , sx, sy )
textImg = 97 + random()*26
textImg.showimage()
object stream = NewStreamFromBuffer( 0 )
ImageWriteImageDataToStream( textImg, stream, 0 )
stream.StreamSetPos(0,0)
string asString = StreamReadAsText( stream, 0, sx*sy )
Result("\n as string:\n\t"+asString)
}
Note that you could create a stream linked to file on disc and, provided you know the starting position in bytes, read from the file directly as well.
来源:https://stackoverflow.com/questions/39719129/how-to-convert-ascii-array-image-to-a-single-string