MATLAB Answers


How can I write an image adapter class for a .bmp image?

I'm trying to develop an image adapter class to accommodate some very large images with blockproc. I've tested the rest of my algorithms with a .tiff image and everything worked as expected but when trying to work with a .bmp file (what will be required for my project) I was unable to successfully write an image adapter class.

Here is the image adapter class that I've written and attempted to use.

classdef bmpAdapter < ImageAdapter
        function obj = bmpAdapter(filename)
            obj.Filename = filename;
            obj.Info = imfinfo(filename);
            obj.ImageSize = [obj.Info.Height obj.Info.Width];
        function result = readRegion(obj, start, count)
            result = imread(obj.Filename,'Index', [1 2 3], ...
                'Info',obj.Info,'PixelRegion', ...
                {[start(1), start(1) + count(1) - 1], ...
                [start(2), start(2) + count(2) - 1]});
        function result = close(obj) %#ok

While using this adapter class with blockproc I'm receiving the following error messages:

Error encountered while executing the readRegion method of the bmpAdapter
class.  The input arguments were:
  region_start: [1  1]
  region_size : [316  348]
The cause of the error was:
Error using imagesci\private\readbmp
Too many input arguments.
Error in imread (line 434)
    [X, map] = feval(, filename, extraArgs{:});
Error in bmpAdapter/readRegion (line 13)
            result = imread(obj.Filename,'Index', [1 2 3], ...
Error in internal.images.AdapterDispatcher/readRegion (line 81)
                data = obj.Adapter.readRegion(region_start, region_size);
Error in blockproc>getBlock (line 788)
    source_data = source.readRegion(...
Error in blockproc (line 282)
block_struct = getBlock(source_dispatcher,block_struct,1,1,options);

I've gone through the following tutorial but haven't had much luck.

Based on the error messages that I'm receiving my method is properly determining the starting positions to read the image data. Any help would be greatly appreciated.




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1 Answer

Answer by Walter Roberson
on 19 May 2013
 Accepted Answer

Those Name/Value pairs are defined for TIFF only. BMP is not defined with any Name/Value pairs, so you will need to strip them out before calling imread()


Note: this does mean that if you want to read portions of a large BMP, then you might need to add complete BMP file format processing code, possibly written in another language.

I removed the Name/Value pairs and am now running into the issue of reading the entire image, thus generating an error. So basically I won't be able to use the imread() function. Does MATLAB provide any other means of reading the specific pixel information or will I have to write a separate function for reading the image information myself?

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