# Copyright 2013 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import matplotlib
matplotlib.use('Agg')
import its.error
import pylab
import sys
import Image
import numpy
import math
import unittest
import cStringIO
import scipy.stats
import copy
DEFAULT_YUV_TO_RGB_CCM = numpy.matrix([
[1.000, 0.000, 1.402],
[1.000, -0.344, -0.714],
[1.000, 1.772, 0.000]])
DEFAULT_YUV_OFFSETS = numpy.array([0, 128, 128])
DEFAULT_GAMMA_LUT = numpy.array(
[math.floor(65535 * math.pow(i/65535.0, 1/2.2) + 0.5)
for i in xrange(65536)])
DEFAULT_INVGAMMA_LUT = numpy.array(
[math.floor(65535 * math.pow(i/65535.0, 2.2) + 0.5)
for i in xrange(65536)])
MAX_LUT_SIZE = 65536
def convert_capture_to_rgb_image(cap,
ccm_yuv_to_rgb=DEFAULT_YUV_TO_RGB_CCM,
yuv_off=DEFAULT_YUV_OFFSETS,
props=None):
"""Convert a captured image object to a RGB image.
Args:
cap: A capture object as returned by its.device.do_capture.
ccm_yuv_to_rgb: (Optional) the 3x3 CCM to convert from YUV to RGB.
yuv_off: (Optional) offsets to subtract from each of Y,U,V values.
props: (Optional) camera properties object (of static values);
required for processing raw images.
Returns:
RGB float-3 image array, with pixel values in [0.0, 1.0].
"""
w = cap["width"]
h = cap["height"]
if cap["format"] == "raw10":
assert(props is not None)
cap = unpack_raw10_capture(cap, props)
if cap["format"] == "raw12":
assert(props is not None)
cap = unpack_raw12_capture(cap, props)
if cap["format"] == "yuv":
y = cap["data"][0:w*h]
u = cap["data"][w*h:w*h*5/4]
v = cap["data"][w*h*5/4:w*h*6/4]
return convert_yuv420_planar_to_rgb_image(y, u, v, w, h)
elif cap["format"] == "jpeg":
return decompress_jpeg_to_rgb_image(cap["data"])
elif cap["format"] == "raw":
assert(props is not None)
r,gr,gb,b = convert_capture_to_planes(cap, props)
return convert_raw_to_rgb_image(r,gr,gb,b, props, cap["metadata"])
else:
raise its.error.Error('Invalid format %s' % (cap["format"]))
def unpack_rawstats_capture(cap):
"""Unpack a rawStats capture to the mean and variance images.
Args:
cap: A capture object as returned by its.device.do_capture.
Returns:
Tuple (mean_image var_image) of float-4 images, with non-normalized
pixel values computed from the RAW16 images on the device
"""
assert(cap["format"] == "rawStats")
w = cap["width"]
h = cap["height"]
img = numpy.ndarray(shape=(2*h*w*4,), dtype='<f', buffer=cap["data"])
analysis_image = img.reshape(2,h,w,4)
mean_image = analysis_image[0,:,:,:].reshape(h,w,4)
var_image = analysis_image[1,:,:,:].reshape(h,w,4)
return mean_image, var_image
def unpack_raw10_capture(cap, props):
"""Unpack a raw-10 capture to a raw-16 capture.
Args:
cap: A raw-10 capture object.
props: Camera properties object.
Returns:
New capture object with raw-16 data.
"""
# Data is packed as 4x10b pixels in 5 bytes, with the first 4 bytes holding
# the MSPs of the pixels, and the 5th byte holding 4x2b LSBs.
w,h = cap["width"], cap["height"]
if w % 4 != 0:
raise its.error.Error('Invalid raw-10 buffer width')
cap = copy.deepcopy(cap)
cap["data"] = unpack_raw10_image(cap["data"].reshape(h,w*5/4))
cap["format"] = "raw"
return cap
def unpack_raw10_image(img):
"""Unpack a raw-10 image to a raw-16 image.
Output image will have the 10 LSBs filled in each 16b word, and the 6 MSBs
will be set to zero.
Args:
img: A raw-10 image, as a uint8 numpy array.
Returns:
Image as a uint16 numpy array, with all row padding stripped.
"""
if img.shape[1] % 5 != 0:
raise its.error.Error('Invalid raw-10 buffer width')
w = img.shape[1]*4/5
h = img.shape[0]
# Cut out the 4x8b MSBs and shift to bits [9:2] in 16b words.
msbs = numpy.delete(img, numpy.s_[4::5], 1)
msbs = msbs.astype(numpy.uint16)
msbs = numpy.left_shift(msbs, 2)
msbs = msbs.reshape(h,w)
# Cut out the 4x2b LSBs and put each in bits [1:0] of their own 8b words.
lsbs = img[::, 4::5].reshape(h,w/4)
lsbs = numpy.right_shift(
numpy.packbits(numpy.unpackbits(lsbs).reshape(h,w/4,4,2),3), 6)
lsbs = lsbs.reshape(h,w)
# Fuse the MSBs and LSBs back together
img16 = numpy.bitwise_or(msbs, lsbs).reshape(h,w)
return img16
def unpack_raw12_capture(cap, props):
"""Unpack a raw-12 capture to a raw-16 capture.
Args:
cap: A raw-12 capture object.
props: Camera properties object.
Returns:
New capture object with raw-16 data.
"""
# Data is packed as 4x10b pixels in 5 bytes, with the first 4 bytes holding
# the MSBs of the pixels, and the 5th byte holding 4x2b LSBs.
w,h = cap["width"], cap["height"]
if w % 2 != 0:
raise its.error.Error('Invalid raw-12 buffer width')
cap = copy.deepcopy(cap)
cap["data"] = unpack_raw12_image(cap["data"].reshape(h,w*3/2))
cap["format"] = "raw"
return cap
def unpack_raw12_image(img):
"""Unpack a raw-12 image to a raw-16 image.
Output image will have the 12 LSBs filled in each 16b word, and the 4 MSBs
will be set to zero.
Args:
img: A raw-12 image, as a uint8 numpy array.
Returns:
Image as a uint16 numpy array, with all row padding stripped.
"""
if img.shape[1] % 3 != 0:
raise its.error.Error('Invalid raw-12 buffer width')
w = img.shape[1]*2/3
h = img.shape[0]
# Cut out the 2x8b MSBs and shift to bits [11:4] in 16b words.
msbs = numpy.delete(img, numpy.s_[2::3], 1)
msbs = msbs.astype(numpy.uint16)
msbs = numpy.left_shift(msbs, 4)
msbs = msbs.reshape(h,w)
# Cut out the 2x4b LSBs and put each in bits [3:0] of their own 8b words.
lsbs = img[::, 2::3].reshape(h,w/2)
lsbs = numpy.right_shift(
numpy.packbits(numpy.unpackbits(lsbs).reshape(h,w/2,2,4),3), 4)
lsbs = lsbs.reshape(h,w)
# Fuse the MSBs and LSBs back together
img16 = numpy.bitwise_or(msbs, lsbs).reshape(h,w)
return img16
def convert_capture_to_planes(cap, props=None):
"""Convert a captured image object to separate image planes.
Decompose an image into multiple images, corresponding to different planes.
For YUV420 captures ("yuv"):
Returns Y,U,V planes, where the Y plane is full-res and the U,V planes
are each 1/2 x 1/2 of the full res.
For Bayer captures ("raw" or "raw10"):
Returns planes in the order R,Gr,Gb,B, regardless of the Bayer pattern
layout. Each plane is 1/2 x 1/2 of the full res.
For JPEG captures ("jpeg"):
Returns R,G,B full-res planes.
Args:
cap: A capture object as returned by its.device.do_capture.
props: (Optional) camera properties object (of static values);
required for processing raw images.
Returns:
A tuple of float numpy arrays (one per plane), consisting of pixel
values in the range [0.0, 1.0].
"""
w = cap["width"]
h = cap["height"]
if cap["format"] == "raw10":
assert(props is not None)
cap = unpack_raw10_capture(cap, props)
if cap["format"] == "raw12":
assert(props is not None)
cap = unpack_raw12_capture(cap, props)
if cap["format"] == "yuv":
y = cap["data"][0:w*h]
u = cap["data"][w*h:w*h*5/4]
v = cap["data"][w*h*5/4:w*h*6/4]
return ((y.astype(numpy.float32) / 255.0).reshape(h, w, 1),
(u.astype(numpy.float32) / 255.0).reshape(h/2, w/2, 1),
(v.astype(numpy.float32) / 255.0).reshape(h/2, w/2, 1))
elif cap["format"] == "jpeg":
rgb = decompress_jpeg_to_rgb_image(cap["data"]).reshape(w*h*3)
return (rgb[::3].reshape(h,w,1),
rgb[1::3].reshape(h,w,1),
rgb[2::3].reshape(h,w,1))
elif cap["format"] == "raw":
assert(props is not None)
white_level = float(props['android.sensor.info.whiteLevel'])
img = numpy.ndarray(shape=(h*w,), dtype='<u2',
buffer=cap["data"][0:w*h*2])
img = img.astype(numpy.float32).reshape(h,w) / white_level
# Crop the raw image to the active array region.
if props.has_key("android.sensor.info.activeArraySize") \
and props["android.sensor.info.activeArraySize"] is not None \
and props.has_key("android.sensor.info.pixelArraySize") \
and props["android.sensor.info.pixelArraySize"] is not None:
# Note that the Rect class is defined such that the left,top values
# are "inside" while the right,bottom values are "outside"; that is,
# it's inclusive of the top,left sides only. So, the width is
# computed as right-left, rather than right-left+1, etc.
wfull = props["android.sensor.info.pixelArraySize"]["width"]
hfull = props["android.sensor.info.pixelArraySize"]["height"]
xcrop = props["android.sensor.info.activeArraySize"]["left"]
ycrop = props["android.sensor.info.activeArraySize"]["top"]
wcrop = props["android.sensor.info.activeArraySize"]["right"]-xcrop
hcrop = props["android.sensor.info.activeArraySize"]["bottom"]-ycrop
assert(wfull >= wcrop >= 0)
assert(hfull >= hcrop >= 0)
assert(wfull - wcrop >= xcrop >= 0)
assert(hfull - hcrop >= ycrop >= 0)
if w == wfull and h == hfull:
# Crop needed; extract the center region.
img = img[ycrop:ycrop+hcrop,xcrop:xcrop+wcrop]
w = wcrop
h = hcrop
elif w == wcrop and h == hcrop:
# No crop needed; image is already cropped to the active array.
None
else:
raise its.error.Error('Invalid image size metadata')
# Separate the image planes.
imgs = [img[::2].reshape(w*h/2)[::2].reshape(h/2,w/2,1),
img[::2].reshape(w*h/2)[1::2].reshape(h/2,w/2,1),
img[1::2].reshape(w*h/2)[::2].reshape(h/2,w/2,1),
img[1::2].reshape(w*h/2)[1::2].reshape(h/2,w/2,1)]
idxs = get_canonical_cfa_order(props)
return [imgs[i] for i in idxs]
else:
raise its.error.Error('Invalid format %s' % (cap["format"]))
def get_canonical_cfa_order(props):
"""Returns a mapping from the Bayer 2x2 top-left grid in the CFA to
the standard order R,Gr,Gb,B.
Args:
props: Camera properties object.
Returns:
List of 4 integers, corresponding to the positions in the 2x2 top-
left Bayer grid of R,Gr,Gb,B, where the 2x2 grid is labeled as
0,1,2,3 in row major order.
"""
# Note that raw streams aren't croppable, so the cropRegion doesn't need
# to be considered when determining the top-left pixel color.
cfa_pat = props['android.sensor.info.colorFilterArrangement']
if cfa_pat == 0:
# RGGB
return [0,1,2,3]
elif cfa_pat == 1:
# GRBG
return [1,0,3,2]
elif cfa_pat == 2:
# GBRG
return [2,3,0,1]
elif cfa_pat == 3:
# BGGR
return [3,2,1,0]
else:
raise its.error.Error("Not supported")
def get_gains_in_canonical_order(props, gains):
"""Reorders the gains tuple to the canonical R,Gr,Gb,B order.
Args:
props: Camera properties object.
gains: List of 4 values, in R,G_even,G_odd,B order.
Returns:
List of gains values, in R,Gr,Gb,B order.
"""
cfa_pat = props['android.sensor.info.colorFilterArrangement']
if cfa_pat in [0,1]:
# RGGB or GRBG, so G_even is Gr
return gains
elif cfa_pat in [2,3]:
# GBRG or BGGR, so G_even is Gb
return [gains[0], gains[2], gains[1], gains[3]]
else:
raise its.error.Error("Not supported")
def convert_raw_to_rgb_image(r_plane, gr_plane, gb_plane, b_plane,
props, cap_res):
"""Convert a Bayer raw-16 image to an RGB image.
Includes some extremely rudimentary demosaicking and color processing
operations; the output of this function shouldn't be used for any image
quality analysis.
Args:
r_plane,gr_plane,gb_plane,b_plane: Numpy arrays for each color plane
in the Bayer image, with pixels in the [0.0, 1.0] range.
props: Camera properties object.
cap_res: Capture result (metadata) object.
Returns:
RGB float-3 image array, with pixel values in [0.0, 1.0]
"""
# Values required for the RAW to RGB conversion.
assert(props is not None)
white_level = float(props['android.sensor.info.whiteLevel'])
black_levels = props['android.sensor.blackLevelPattern']
gains = cap_res['android.colorCorrection.gains']
ccm = cap_res['android.colorCorrection.transform']
# Reorder black levels and gains to R,Gr,Gb,B, to match the order
# of the planes.
black_levels = [get_black_level(i,props,cap_res) for i in range(4)]
gains = get_gains_in_canonical_order(props, gains)
# Convert CCM from rational to float, as numpy arrays.
ccm = numpy.array(its.objects.rational_to_float(ccm)).reshape(3,3)
# Need to scale the image back to the full [0,1] range after subtracting
# the black level from each pixel.
scale = white_level / (white_level - max(black_levels))
# Three-channel black levels, normalized to [0,1] by white_level.
black_levels = numpy.array([b/white_level for b in [
black_levels[i] for i in [0,1,3]]])
# Three-channel gains.
gains = numpy.array([gains[i] for i in [0,1,3]])
h,w = r_plane.shape[:2]
img = numpy.dstack([r_plane,(gr_plane+gb_plane)/2.0,b_plane])
img = (((img.reshape(h,w,3) - black_levels) * scale) * gains).clip(0.0,1.0)
img = numpy.dot(img.reshape(w*h,3), ccm.T).reshape(h,w,3).clip(0.0,1.0)
return img
def get_black_level(chan, props, cap_res):
"""Return the black level to use for a given capture.
Uses a dynamic value from the capture result if available, else falls back
to the static global value in the camera characteristics.
Args:
chan: The channel index, in canonical order (R, Gr, Gb, B).
props: The camera properties object.
cap_res: A capture result object.
Returns:
The black level value for the specified channel.
"""
if cap_res.has_key("android.sensor.dynamicBlackLevel"):
black_levels = cap_res["android.sensor.dynamicBlackLevel"]
else:
black_levels = props['android.sensor.blackLevelPattern']
idxs = its.image.get_canonical_cfa_order(props)
ordered_black_levels = [black_levels[i] for i in idxs]
return ordered_black_levels[chan]
def convert_yuv420_planar_to_rgb_image(y_plane, u_plane, v_plane,
w, h,
ccm_yuv_to_rgb=DEFAULT_YUV_TO_RGB_CCM,
yuv_off=DEFAULT_YUV_OFFSETS):
"""Convert a YUV420 8-bit planar image to an RGB image.
Args:
y_plane: The packed 8-bit Y plane.
u_plane: The packed 8-bit U plane.
v_plane: The packed 8-bit V plane.
w: The width of the image.
h: The height of the image.
ccm_yuv_to_rgb: (Optional) the 3x3 CCM to convert from YUV to RGB.
yuv_off: (Optional) offsets to subtract from each of Y,U,V values.
Returns:
RGB float-3 image array, with pixel values in [0.0, 1.0].
"""
y = numpy.subtract(y_plane, yuv_off[0])
u = numpy.subtract(u_plane, yuv_off[1]).view(numpy.int8)
v = numpy.subtract(v_plane, yuv_off[2]).view(numpy.int8)
u = u.reshape(h/2, w/2).repeat(2, axis=1).repeat(2, axis=0)
v = v.reshape(h/2, w/2).repeat(2, axis=1).repeat(2, axis=0)
yuv = numpy.dstack([y, u.reshape(w*h), v.reshape(w*h)])
flt = numpy.empty([h, w, 3], dtype=numpy.float32)
flt.reshape(w*h*3)[:] = yuv.reshape(h*w*3)[:]
flt = numpy.dot(flt.reshape(w*h,3), ccm_yuv_to_rgb.T).clip(0, 255)
rgb = numpy.empty([h, w, 3], dtype=numpy.uint8)
rgb.reshape(w*h*3)[:] = flt.reshape(w*h*3)[:]
return rgb.astype(numpy.float32) / 255.0
def load_rgb_image(fname):
"""Load a standard image file (JPG, PNG, etc.).
Args:
fname: The path of the file to load.
Returns:
RGB float-3 image array, with pixel values in [0.0, 1.0].
"""
img = Image.open(fname)
w = img.size[0]
h = img.size[1]
a = numpy.array(img)
if len(a.shape) == 3 and a.shape[2] == 3:
# RGB
return a.reshape(h,w,3) / 255.0
elif len(a.shape) == 2 or len(a.shape) == 3 and a.shape[2] == 1:
# Greyscale; convert to RGB
return a.reshape(h*w).repeat(3).reshape(h,w,3) / 255.0
else:
raise its.error.Error('Unsupported image type')
def load_yuv420_to_rgb_image(yuv_fname,
w, h,
layout="planar",
ccm_yuv_to_rgb=DEFAULT_YUV_TO_RGB_CCM,
yuv_off=DEFAULT_YUV_OFFSETS):
"""Load a YUV420 image file, and return as an RGB image.
Supported layouts include "planar" and "nv21". The "yuv" formatted captures
returned from the device via do_capture are in the "planar" layout; other
layouts may only be needed for loading files from other sources.
Args:
yuv_fname: The path of the YUV420 file.
w: The width of the image.
h: The height of the image.
layout: (Optional) the layout of the YUV data (as a string).
ccm_yuv_to_rgb: (Optional) the 3x3 CCM to convert from YUV to RGB.
yuv_off: (Optional) offsets to subtract from each of Y,U,V values.
Returns:
RGB float-3 image array, with pixel values in [0.0, 1.0].
"""
with open(yuv_fname, "rb") as f:
if layout == "planar":
# Plane of Y, plane of V, plane of U.
y = numpy.fromfile(f, numpy.uint8, w*h, "")
v = numpy.fromfile(f, numpy.uint8, w*h/4, "")
u = numpy.fromfile(f, numpy.uint8, w*h/4, "")
elif layout == "nv21":
# Plane of Y, plane of interleaved VUVUVU...
y = numpy.fromfile(f, numpy.uint8, w*h, "")
vu = numpy.fromfile(f, numpy.uint8, w*h/2, "")
v = vu[0::2]
u = vu[1::2]
else:
raise its.error.Error('Unsupported image layout')
return convert_yuv420_planar_to_rgb_image(
y,u,v,w,h,ccm_yuv_to_rgb,yuv_off)
def load_yuv420_planar_to_yuv_planes(yuv_fname, w, h):
"""Load a YUV420 planar image file, and return Y, U, and V plane images.
Args:
yuv_fname: The path of the YUV420 file.
w: The width of the image.
h: The height of the image.
Returns:
Separate Y, U, and V images as float-1 Numpy arrays, pixels in [0,1].
Note that pixel (0,0,0) is not black, since U,V pixels are centered at
0.5, and also that the Y and U,V plane images returned are different
sizes (due to chroma subsampling in the YUV420 format).
"""
with open(yuv_fname, "rb") as f:
y = numpy.fromfile(f, numpy.uint8, w*h, "")
v = numpy.fromfile(f, numpy.uint8, w*h/4, "")
u = numpy.fromfile(f, numpy.uint8, w*h/4, "")
return ((y.astype(numpy.float32) / 255.0).reshape(h, w, 1),
(u.astype(numpy.float32) / 255.0).reshape(h/2, w/2, 1),
(v.astype(numpy.float32) / 255.0).reshape(h/2, w/2, 1))
def decompress_jpeg_to_rgb_image(jpeg_buffer):
"""Decompress a JPEG-compressed image, returning as an RGB image.
Args:
jpeg_buffer: The JPEG stream.
Returns:
A numpy array for the RGB image, with pixels in [0,1].
"""
img = Image.open(cStringIO.StringIO(jpeg_buffer))
w = img.size[0]
h = img.size[1]
return numpy.array(img).reshape(h,w,3) / 255.0
def apply_lut_to_image(img, lut):
"""Applies a LUT to every pixel in a float image array.
Internally converts to a 16b integer image, since the LUT can work with up
to 16b->16b mappings (i.e. values in the range [0,65535]). The lut can also
have fewer than 65536 entries, however it must be sized as a power of 2
(and for smaller luts, the scale must match the bitdepth).
For a 16b lut of 65536 entries, the operation performed is:
lut[r * 65535] / 65535 -> r'
lut[g * 65535] / 65535 -> g'
lut[b * 65535] / 65535 -> b'
For a 10b lut of 1024 entries, the operation becomes:
lut[r * 1023] / 1023 -> r'
lut[g * 1023] / 1023 -> g'
lut[b * 1023] / 1023 -> b'
Args:
img: Numpy float image array, with pixel values in [0,1].
lut: Numpy table encoding a LUT, mapping 16b integer values.
Returns:
Float image array after applying LUT to each pixel.
"""
n = len(lut)
if n <= 0 or n > MAX_LUT_SIZE or (n & (n - 1)) != 0:
raise its.error.Error('Invalid arg LUT size: %d' % (n))
m = float(n-1)
return (lut[(img * m).astype(numpy.uint16)] / m).astype(numpy.float32)
def apply_matrix_to_image(img, mat):
"""Multiplies a 3x3 matrix with each float-3 image pixel.
Each pixel is considered a column vector, and is left-multiplied by
the given matrix:
[ ] r r'
[ mat ] * g -> g'
[ ] b b'
Args:
img: Numpy float image array, with pixel values in [0,1].
mat: Numpy 3x3 matrix.
Returns:
The numpy float-3 image array resulting from the matrix mult.
"""
h = img.shape[0]
w = img.shape[1]
img2 = numpy.empty([h, w, 3], dtype=numpy.float32)
img2.reshape(w*h*3)[:] = (numpy.dot(img.reshape(h*w, 3), mat.T)
).reshape(w*h*3)[:]
return img2
def get_image_patch(img, xnorm, ynorm, wnorm, hnorm):
"""Get a patch (tile) of an image.
Args:
img: Numpy float image array, with pixel values in [0,1].
xnorm,ynorm,wnorm,hnorm: Normalized (in [0,1]) coords for the tile.
Returns:
Float image array of the patch.
"""
hfull = img.shape[0]
wfull = img.shape[1]
xtile = math.ceil(xnorm * wfull)
ytile = math.ceil(ynorm * hfull)
wtile = math.floor(wnorm * wfull)
htile = math.floor(hnorm * hfull)
return img[ytile:ytile+htile,xtile:xtile+wtile,:].copy()
def compute_image_means(img):
"""Calculate the mean of each color channel in the image.
Args:
img: Numpy float image array, with pixel values in [0,1].
Returns:
A list of mean values, one per color channel in the image.
"""
means = []
chans = img.shape[2]
for i in xrange(chans):
means.append(numpy.mean(img[:,:,i], dtype=numpy.float64))
return means
def compute_image_variances(img):
"""Calculate the variance of each color channel in the image.
Args:
img: Numpy float image array, with pixel values in [0,1].
Returns:
A list of mean values, one per color channel in the image.
"""
variances = []
chans = img.shape[2]
for i in xrange(chans):
variances.append(numpy.var(img[:,:,i], dtype=numpy.float64))
return variances
def compute_image_snrs(img):
"""Calculate the SNR (db) of each color channel in the image.
Args:
img: Numpy float image array, with pixel values in [0,1].
Returns:
A list of SNR value, one per color channel in the image.
"""
means = compute_image_means(img)
variances = compute_image_variances(img)
std_devs = [math.sqrt(v) for v in variances]
snr = [20 * math.log10(m/s) for m,s in zip(means, std_devs)]
return snr
def write_image(img, fname, apply_gamma=False):
"""Save a float-3 numpy array image to a file.
Supported formats: PNG, JPEG, and others; see PIL docs for more.
Image can be 3-channel, which is interpreted as RGB, or can be 1-channel,
which is greyscale.
Can optionally specify that the image should be gamma-encoded prior to
writing it out; this should be done if the image contains linear pixel
values, to make the image look "normal".
Args:
img: Numpy image array data.
fname: Path of file to save to; the extension specifies the format.
apply_gamma: (Optional) apply gamma to the image prior to writing it.
"""
if apply_gamma:
img = apply_lut_to_image(img, DEFAULT_GAMMA_LUT)
(h, w, chans) = img.shape
if chans == 3:
Image.fromarray((img * 255.0).astype(numpy.uint8), "RGB").save(fname)
elif chans == 1:
img3 = (img * 255.0).astype(numpy.uint8).repeat(3).reshape(h,w,3)
Image.fromarray(img3, "RGB").save(fname)
else:
raise its.error.Error('Unsupported image type')
def downscale_image(img, f):
"""Shrink an image by a given integer factor.
This function computes output pixel values by averaging over rectangular
regions of the input image; it doesn't skip or sample pixels, and all input
image pixels are evenly weighted.
If the downscaling factor doesn't cleanly divide the width and/or height,
then the remaining pixels on the right or bottom edge are discarded prior
to the downscaling.
Args:
img: The input image as an ndarray.
f: The downscaling factor, which should be an integer.
Returns:
The new (downscaled) image, as an ndarray.
"""
h,w,chans = img.shape
f = int(f)
assert(f >= 1)
h = (h/f)*f
w = (w/f)*f
img = img[0:h:,0:w:,::]
chs = []
for i in xrange(chans):
ch = img.reshape(h*w*chans)[i::chans].reshape(h,w)
ch = ch.reshape(h,w/f,f).mean(2).reshape(h,w/f)
ch = ch.T.reshape(w/f,h/f,f).mean(2).T.reshape(h/f,w/f)
chs.append(ch.reshape(h*w/(f*f)))
img = numpy.vstack(chs).T.reshape(h/f,w/f,chans)
return img
def compute_image_sharpness(img):
"""Calculate the sharpness of input image.
Args:
img: Numpy float RGB/luma image array, with pixel values in [0,1].
Returns:
A sharpness estimation value based on the average of gradient magnitude.
Larger value means the image is sharper.
"""
chans = img.shape[2]
assert(chans == 1 or chans == 3)
luma = img
if (chans == 3):
luma = 0.299 * img[:,:,0] + 0.587 * img[:,:,1] + 0.114 * img[:,:,2]
[gy, gx] = numpy.gradient(luma)
return numpy.average(numpy.sqrt(gy*gy + gx*gx))
class __UnitTest(unittest.TestCase):
"""Run a suite of unit tests on this module.
"""
# TODO: Add more unit tests.
def test_apply_matrix_to_image(self):
"""Unit test for apply_matrix_to_image.
Test by using a canned set of values on a 1x1 pixel image.
[ 1 2 3 ] [ 0.1 ] [ 1.4 ]
[ 4 5 6 ] * [ 0.2 ] = [ 3.2 ]
[ 7 8 9 ] [ 0.3 ] [ 5.0 ]
mat x y
"""
mat = numpy.array([[1,2,3],[4,5,6],[7,8,9]])
x = numpy.array([0.1,0.2,0.3]).reshape(1,1,3)
y = apply_matrix_to_image(x, mat).reshape(3).tolist()
y_ref = [1.4,3.2,5.0]
passed = all([math.fabs(y[i] - y_ref[i]) < 0.001 for i in xrange(3)])
self.assertTrue(passed)
def test_apply_lut_to_image(self):
""" Unit test for apply_lut_to_image.
Test by using a canned set of values on a 1x1 pixel image. The LUT will
simply double the value of the index:
lut[x] = 2*x
"""
lut = numpy.array([2*i for i in xrange(65536)])
x = numpy.array([0.1,0.2,0.3]).reshape(1,1,3)
y = apply_lut_to_image(x, lut).reshape(3).tolist()
y_ref = [0.2,0.4,0.6]
passed = all([math.fabs(y[i] - y_ref[i]) < 0.001 for i in xrange(3)])
self.assertTrue(passed)
if __name__ == '__main__':
unittest.main()