Stranica 138 [138]
cn A B 7
18) A matrix of values is created by subdividing the image of the standards by the number
entered and determining the average X, Y and Z values for each of these. Double left¬
clicking on the "sample" thumbnail (Figure 3-30 and Figure 3-31) opens a window
(Bl.sample), which aids in the visualisation of the areas being sampled to create this
matrix of values. A slider is provided to adjust this area. Thus in Figure 3-30, 50% of the
area of each target is sampled. In Figure 3-31 this has been adjusted to 40%, to ensure
the area sampled is within the targets (as these are further apart and vary in shape).
Adjust as necessary for the available Spectralon diffuse reflectance standards.
Generating the colour calibration matrix
19) Click on the “viscalib” tab to the right. Column D on the left carries out the analysis and
generates the calibration matrix from the Macbeth chart (Figure 3-32). The image at D1
is automatically carried over from the “markup” tab.
input linear | markup | viscalb | uvicalib align | specden falsecolour uvistray | uvikm | vilstray ! vilkm results +
V H- calibrate visible reflectance image a i
2 m0 label | visible reflectance |
v v
targets_label | visible reflectance with calibration targets, colour-calibrated
S targets !
object label | visible reflectance of object, colour-calibrated
macbeth | Pick a Macbeth data file: macbeth_lab_d65.mat Ő D8.sample - 50% =
= =| Elle view Help
mode input LUT: [linear input, set brightness from chart © > Shane wes 08 75 By Kt ci
linearising_lut
Image, unsigned
gli ( 514, 16) — 110 109 146 Magnification 1:2
a ts sans, 256 pots, range [0,25], vrange (0, 0.996076]
is M |0.290469 (0.674184 (0.0158778
v
0.543422 (1.51308 | 0.0303436
~0.180834 0.143996 | 1.04073
scale | 1.325384
ava_dE76 | 4.892412
worst patch | Blue (patch 13, 13.174 de)
input.Find_calib_item.action D1
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Figure 3-32
20) Double left-clicking on the “sample” thumbnail (Figure 3-32) opens a window
(D8.sample), which aids in the visualisation of the areas being sampled to create the
calibration matrix. A slider is provided to adjust this area if necessary.
21) Check that the file “macbeth_lab_d65.mat” has been selected in the “Pick a Macbeth
data file” option (this should be loaded automatically on loading the workspace), (Figure
3-32).
22) Check that the “Linear output, set brightness from chart” option has been selected from
the “Input LUT” menu in D8, (Figure 3-32). This sets the brightness or luminance of the
image from the grey scale on the Macbeth chart.
Version No. 1.0 130 Date : 14/10/2013