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Method for exposing the raw data #104

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Method for exposing the raw data #104

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23f4a82
Nealy getting the reading of the raw data to work
paalge Oct 29, 2015
6bf6de9
Working raw data getter. Returns a numpy array
paalge Oct 29, 2015
ae7876c
Removed dependency on numpy
paalge Oct 29, 2015
bed08b4
Fixed the error handling for none 4 colour images
paalge Oct 29, 2015
657a9b5
catch ValueError
paalge Oct 29, 2015
451f7dc
Fixed line length in comment
paalge Oct 29, 2015
a2c8b90
Removed trailing whitespaces
paalge Oct 29, 2015
e585b6d
Added get_3_col_raw and fixed the returned image from get_4_col_raw
paalge Nov 11, 2015
e7b6c5a
Moved the common code into new function
paalge Dec 14, 2015
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52 changes: 52 additions & 0 deletions rawkit/raw.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,58 @@ def save_thumb(self, filename=None):
self.libraw.libraw_dcraw_thumb_writer(
self.data, filename.encode('ascii'))

def get_4_col_raw(self):
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Another thing I'm thinking (though this doesn't have to be done right now by any means, I just wanted to comment while I was thinking about it so that it was documented somewhere) is that the public facing API method for this should just work for all types of raws (regardless of how many channels there are). @campaul and I will probably sit down sometime this weekend and figure out a more unified API (including return values and types) for all methods that return image data like this. Will advise.

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Hi.

It is easy to change this to the other case (with only 3 colours), as the data then is in color3_image and not in color4_image. Though before I modify this I would like to know what the return types should be. In my mind we should return something that is 2D, as this removes the need to pass along height and width.

"""
Read the 4 colour raw data
The returned numpy array is (given colour RGGB)
---------
R B R B ...
G B G B ...
R B R B ....
. . . . .
. . . . .
. . . . .
--------


Returns:
list of list: 4 colour data of the image in unit16.
(width x height)
str : colour channel description (ie. RGGB, RGBG)
"""
# Unpack the data, so that rawdata is populated
self.unpack()
rawdata = self.data.contents.rawdata

# Return None if the image isn't 4 colour, which will happen for some
# cameras

try:
rawdata.color4_image.contents
except ValueError:
return None

# Get image size
iheight = rawdata.sizes.iheight
iwidth = rawdata.sizes.iwidth

# Make pointer to data

data_pointer = ctypes.cast(
rawdata.color4_image.contents,
ctypes.POINTER(ctypes.c_ushort)
)

# make 2D list
data = [[0 for i in range(iheight)] for j in range(iwidth)]
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This might be cleaner, no idea if there's a "standard" way to do this in Python:

data = [None] * iheight * iwidth

It might be a pre-mature optimization either way though. Or I may be completely wrong. Just thinking out loud. @campaul?

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It needs to be 2D, or you'll have to pass height and width on, and let the calling function do the reshape.
From what I understood, list compression is the normal way of initialising this.

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Sounds good then. I think the above will make a 2d list too, but I could be mistaken. If we're going to have to iterate anyways though I think we might as well not preallocate.

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A quick quick test gives it as a 1D.
As for the preallocate, I like it due to the large lists being created, though I don't know what is fastest.

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If we're going to loop and append, 0's though we might as well just loop and append the data. I'm not sure this is actually an optimization, unless Python does some sort of optimization on simple list comprehensions that I don't know about.

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This would probably be more efficient. I'll do some timings later and see for sure.

data = [[] for j in range(iwidth)]

for ii in range(iheight):
    for jj in range(iwidth):
        data[jj].append(data_pointer[ii * iwidth + jj])


for ii in range(iheight):
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Can we change ii and jj to y and x respectively so we're working with Cartesian coordinates?

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These aren't actually coordinates on the image though since there are multiple indexes per pixel.

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They will be coordinates, though you have to interpolate the image first, as in that loop they change between different colour channels.

for jj in range(iwidth):
data[jj][ii] = data_pointer[ii * iwidth + jj]
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This still appears to be subscripting a 2D array; won't this be broken?

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In my test run this works as intended.
Though I'm not sure what you think would be broken?
Line 221 makes a 2D list, which one can index with [][] in line 225

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Oh right, yah, I was misunderstanding a large chunk of our discussion, sorry. I think it's best to make this a 1D list to match the data that we get from LibRaw / elsewhere in rawkit. Not sure though; will consider the API implications of doing this and get back to you. It's not super important right now.


# Return data and colour descriptor
return data, self.data.contents.idata.cdesc

def to_buffer(self):
"""
Convert the image to an RGB buffer.
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