About bitmap array

[doraneko]

I want to read or write a file to keep bitmap array.
Not each jpeg files, but a single file consists of multiple bitmap data.
Each bitmaps are same Height and Width.
Should I use RandomAccessFile or Input/OutputStream ?
Please teach me.:sign0085:

 

[Erel]

How many bitmaps do you want to save this way? If you can hold all bitmaps in memory then it will be easier.

 

[doraneko]

I want to save about 30 to 50 bitmaps as follows.

Dim photo(31) As Bitmap

Please help me.

 

[Erel]

You cannot directly write an array of bitmaps to a file.
You can do something like:
- Create a list.
- Convert each bitmap to a bytes array by writing it to an OutputStream that was initialized with OutputStream.InitializeToBytesArray, and add the bytes array to the list (as single item).
- Save the whole list with RandomAccessFile.WriteObject.

To read the images:
- Read the whole list with RandomAccessFile.ReadObject.
- Convert each bytes array to a bitmap by first creating an InputStream with InputStream.InitializeFromBytesArray and then using Bitmap.Initialize2.

 

[doraneko]

Thank you, Erel.

I can understand about 'write procedure', but can not about 'read procedure'.
Especially, Please teach me how to convert List into InputStream.
And, if I use 'PNG' with WriteToStream and 'Compress' with WriteObject in 'write procedure', Can I reconstruct in 'read procedure' ?

 

[Erel]

RandomAccessObject.WriteObject / ReadObject is responsible for writing and reading the list.

And, if I use 'PNG' with WriteToStream and 'Compress' with WriteObject in 'write procedure', Can I reconstruct in 'read procedure' ?

Yes, it should work fine.

 

[doraneko]

Please teach me, how to convert List to InputStream with buffer, MaxCount and ReadBytes.

 

[Erel]

You can use RandomAccessFile.WriteObject(List1).

 

[doraneko]

For Erel.

You said
To read the images:
- Read the whole list with RandomAccessFile.ReadObject.
- Convert each bytes array to a bitmap by first creating an InputStream with InputStream.InitializeFromBytesArray and then using Bitmap.Initialize2.

Then, I can not understand as follows...

RandomAccessFile1.Initialize(FPath, FileName, True)
List1.Initialize
List1.AddAll(RandomAccessFile1.ReadObject(0))
InputStream1.InitializeFromBytesArray(buffer, 0, buffer.length)?
?? how to convert List1 into InputStream1 ? List1 is buffer ?
InputStream1.ReadBytes(buffer, 0, buffer.length)?
Bitmap1(i).Initialize2(InputStream1)

Please help me.:sign0085:

 

[Erel]

Write the list:
RandomAccessFile.WriteObject(List1, true, 0)

Read the list:
List1 = RandomAccessFile.ReadObject(0)

 

[doraneko]

Thank you, Erel.

' Read the list: List1 = RandomAccessFile.ReadObject(0) ' is a very useful advice.
And next step, How should I do ?

How about buffer for InputStream ?
Is List1.Get needed for InputStream ?
More over, Is InputStream.ReadBytes(buffer, 0, buffer.length) needed?

Although you are too busy, please teach me.

 

[kickaha]

Thank you, Erel.

' Read the list: List1 = RandomAccessFile.ReadObject(0) ' is a very useful advice.
And next step, How should I do ?

How about buffer for InputStream ?
Is List1.Get needed for InputStream ?
More over, Is InputStream.ReadBytes(buffer, 0, buffer.length) needed?

Although you are too busy, please teach me.

To quote an earlier post by Erel

Convert each bytes Array To a Bitmap by first creating an InputStream with InputStream.InitializeFromBytesArray and then using Bitmap.Initialize2.

 

[doraneko]

For Kickaha

I know what you say.
But, I don't know that, List1 is buffer or not
in 'InputStream1.InitializeFromBytesArray '(buffer, 0, buffer.length)'.

More over, 'InputStream1.ReadBytes(buffer, 0, buffer.length)' and/or
'List1.get(i)' is needed or not.

What should I do ?http://www.b4x.com/forum/images/smilies/confused.gif

 

[macerau]

Hi Erel,
Sorry, I'm newbie,
searched a lot on the site but did not see a working example,
Please see if you can complete this routine
Sub SavePhoto (Pt As Bitmap,NewFile As String)
Dim LT As List
Dim RF As RandomAccessFile
RF.Initialize(File.DirAssets , NewFile, True)
LT.Initialize
LT.AddAll(Pt.WriteToStream) ' RF.ReadObject(0) ??

rf.WriteObject(LT, True, 0)
Dim ip As InputStream ?
ip.InitializeFromBytesArray(buffer, 0, buffer.length) ?
?? how To convert List1 into InputStream1 ? List1 Is buffer ?
InputStream1.ReadBytes(buffer, 0, buffer.length)?
B.Initialize2(InputStream1) ?


End Sub

 

[Erel]

Please use [ code ] [ /code ] tags (without spaces) when posting code.

It is usually better to start a new thread for new questions. Do you want to save the image to a file? You do not need to use RandomAccessFile for that.

 

[alfcen]

To Erel,

Sorry to pick this up.

Your method described in post #4 does work, however, it takes about 10 seconds to
save a list containing 30 PNGs (64 x 64 each), and another 10 seconds retrieving one
from the loaded list.

Out of curiosity, which is the bottleneck, InitializeToBytesArray or Read/WriteObject?

 

[Erel]

Have you tried to save the images with KeyValueStore class?

 

[alfcen]

Frankly, I was not aware of such a class. I'll try it.
Anyway, what is it that slows down the routines?

 

[Erel]

Probably the object reading / writing.

 

[alfcen]

Yes, also, if compression is set to False it takes 3 seconds each for saving all images and retrieving one image (i/o 10).