Hello all, just joined (thanks Olivier) and wanted to share a little bit of
code with you in case you thought it useful. I got a canon 7d little while
ago and noticed that the builtin screen indicates with red boxes which
focus points were used. I thought that was interesting so I went trudging
through the exif info to see if I could generate images showing the focus
points as well. this is what i ended up with. grey boxes showing all
focus points. white for subset which were active when the shot was
composed, and red for the ones that were used to take the shot. please
excuse the code duplication, i haven't cleaned up the code yet to deal with
dcraw rotating the image for me. You can just ignore the clauses for
rotatepic==true.
I was thinking that perhaps these values (focuspointwidth,
focuspointheight, focuspointxpos, focuspointypos, activeafpoints, afpoints)
could be exposed more directly. interested in your thoughts.
Jason
class cr2imagewriter():
def __init__(self, imagedata, metadata, filename):
# for exifdatum in metadata.exif_keys:
# print 'exif key %s val %s' % (exifdatum,
metadata[exifdatum].human_value)
# print '11','#' * 80,'\n'
try:
exif_dim = metadata['Exif.Canon.AFInfo'].value[4:6]
focuspointwidth = metadata['Exif.Canon.AFInfo'].value[8:8+19]
focuspointheight = metadata['Exif.Canon.AFInfo'].value[27:27+19]
focuspointxpos = [unpack('=h', pack('=H', i & 0xffff))[0] for i
in metadata['Exif.Canon.AFInfo'].value[46:46+19]]
focuspointypos = [unpack('=h', pack('=H', i & 0xffff))[0] for i
in metadata['Exif.Canon.AFInfo'].value[65:65+19]]
activeafpoints = [unpack('=h', pack('=H', i & 0xffff))[0] for i
in metadata['Exif.Canon.AFInfo'].value[84:85]]
afpoints = [unpack('=h', pack('=H', i & 0xffff))[0] for i in
metadata['Exif.Canon.AFInfo'].value[86:87]]
draw = ImageDraw.Draw(imagedata)
(xsize, ysize) = imagedata.size
print 'my size %dx%d' % (xsize, ysize)
rotatepic = False
if (ysize > xsize):
# dcraw automatically rotates the image it feeds me
# my heuristic for determining this is to check y size vs
xsize
# and then munge my x and y coordinates to scribble
# sideways when i write my rectangles
rotatepic = True
widthadjust = float(exif_dim[0])/float(ysize)
heightadjust = float(exif_dim[1])/float(xsize)
else:
widthadjust = float(exif_dim[0])/float(xsize)
heightadjust = float(exif_dim[1])/float(ysize)
print 'my size2 %dx%d' % (xsize, ysize)
print 'exif_dim %dx%d' % (exif_dim[0], exif_dim[1])
print 'width ratio is %f' % widthadjust
print 'height ratio is %f' % heightadjust
for i in range(0, len(focuspointwidth)):
if 1 == activeafpoints[0]>>i&1:
color = ImageColor.getrgb("red")
else:
if 1 == afpoints[0]>>i&1:
color = ImageColor.getrgb("white")
else:
color = ImageColor.getrgb("grey")
if rotatepic:
draw.rectangle((-((float(focuspointypos[i])/float(heightadjust)))+float(xsize)/2.0,
-(float(focuspointxpos[i])/float(widthadjust))+float(ysize)/2.0,
-((float(focuspointypos[i])/float(heightadjust))+(float(focuspointheight[i])/float(heightadjust)))+float(xsize)/2.0,
-(float(focuspointxpos[i])/float(widthadjust))+(float(focuspointwidth[i])/float(widthadjust))+float(ysize)/2.0),
fill=None, outline=color)
else:
draw.rectangle(((float(focuspointxpos[i])/float(widthadjust))+float(xsize)/2.0,
((-float(focuspointypos[i])/float(heightadjust)))+float(ysize)/2.0,
(float(focuspointxpos[i])/float(widthadjust))+(float(focuspointwidth[i])/float(widthadjust))+float(xsize)/2.0,
(-(float(focuspointypos[i])/float(heightadjust))+(float(focuspointheight[i])/float(heightadjust)))+float(ysize)/2.0),
fill=None, outline=color)
except:
raise
imagedata.save(file(filename, "w"), 'JPEG', quality=85,
optimize=True)
where, earlier in the code:
metadata = pyexiv2.ImageMetadata(pic)
metadata.read()
and
dcraw = subprocess.Popen(['dcraw', '-b', '2.5', '-c', '-w',
'-W', '-v', '-q', '3', pic], stdout=PIPE, universal_newlines=False)
dcrawdata = dcraw.communicate()[0]
print 'name ', pic
print 'dcraw data %d' % len(dcrawdata)
ImageFile.MAXBLOCK = 75000000 # default is 64k
imagedata = Image.open(cStringIO.StringIO(dcrawdata))
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