[gimp-web/testing] Finishing touches and edits on Tone Mapping tutorial from Elle

[Pat David <patdavid src gnome org>]

commit 23068358d391a3c5e3b7568008698ed616c26b5b
Author: Pat David <patdavid gmail com>
Date:   Wed May 4 11:13:49 2016 -0500

    Finishing touches and edits on Tone Mapping tutorial from Elle
    
    Just fixing some emdash spacing errors, downloading tree.png.
    Also fixing all the image swapping with <noscript> options for
    those not usnig Javascript so the page will still render correctly.

 .../Tone_Mapping_Using_GIMP_Levels/index.md        |   51 +++++++++++++++-----
 .../Tone_Mapping_Using_GIMP_Levels/tree.png        |  Bin 0 -> 1320452 bytes
 2 files changed, 39 insertions(+), 12 deletions(-)
---
diff --git a/content/tutorials/Tone_Mapping_Using_GIMP_Levels/index.md 
b/content/tutorials/Tone_Mapping_Using_GIMP_Levels/index.md
index 3809fea..51d15fb 100644
--- a/content/tutorials/Tone_Mapping_Using_GIMP_Levels/index.md
+++ b/content/tutorials/Tone_Mapping_Using_GIMP_Levels/index.md
@@ -24,8 +24,7 @@ A very common editing problem is how to lighten the shadows and midtones of an i
 
 A very common editing problem is how to lighten the shadows and midtones of an image without blowing out the 
highlights, which problem is very often encountered when dealing with photographs of scenes lit by direct 
sunlight. Precanned algorithms for accomplishing this task are often referred to as "shadow recovery" 
algorithms. But really these algorithms are special-purpose tone-mapping algorithms, which sometimes work 
pretty well, and sometimes not so well, depending on the algorithm, the image, and your artistic intentions 
for the image.
 
-This step-by-step tutorial shows you how to use GIMP's unbounded floating point "Colors/Exposure" operation 
to recover shadow information — that is, add one or more stops of positive exposure compensation to an 
image's shadows and midtones — without blowing out or unduly compressing the image highlights. The procedure 
is completely "hand-tunable" using masks and layers, and is as close as you can get to non-destructive image 
editing using high bit depth GIMP 2.9/2.10.
-
+This step-by-step tutorial shows you how to use GIMP's unbounded floating point "Colors/Exposure" operation 
to recover shadow information&mdash;that is, add one or more stops of positive exposure compensation to an 
image's shadows and midtones&mdash;without blowing out or unduly compressing the image highlights. The 
procedure is completely "hand-tunable" using masks and layers, and is as close as you can get to 
non-destructive image editing using high bit depth GIMP 2.9/2.10.
 
 <figure>
 <img src='power-lines.jpg' alt='power-lines'>
@@ -49,7 +48,7 @@ Scene-referred interpolated raw file.
 <!-- 
 Accepted wisdom is that Curves provides more versatility than Levels for modifying image tonality. Of course 
you can use Curves to accomplish somewhat similar results to the procedure described in this tutorial. But 
GIMP Curves is a highly destructive editing operation, immediately "baking" the resulting tonality into the 
layer on which Curves is done, clipping any out of gamut RGB values, and leaving you with no way to fine-tune 
the results without starting over. -->
 
-Hight bit depth GIMP is my primary image editor, and I've used the procedure described below for the last 
couple of years as my "go to" way to modify image tonality. The same general procedure can be used to darken 
as well as lighten portions of an image, again controlling the effect using a layer mask. This isn't exactly 
nondestructive editing because at some point you need to make a "New from Visible" layer. But unlike using 
Curves, using high bit depth GIMP's floating point "Colors/Exposure" doesn't clip RGB channel values and 
allows you to fine-tune the results by modifying and remodifying the layer mask until you are completely 
happy with the resulting tonality.
+Hight bit depth GIMP is my primary image editor, and I've used the procedure described below for the last 
couple of years as my "go to" way to modify image tonality. The same general procedure can be used to darken 
as well as lighten portions of an image, again controlling the effect using a layer mask. This isn't exactly 
nondestructive editing because at some point you need to make a "New from Visible" layer. But unlike using 
Curves, using high bit depth GIMP's floating point "Colors/Exposure" doesn't clip RGB channel values and 
allows you to fine-tune the results by modifying and re-modifying the layer mask until you are completely 
happy with the resulting tonality.
 
 
 ## A step-by-step example showing how to recover shadow information using high bit depth GIMP's floating 
point "Colors/Exposure"
@@ -70,23 +69,21 @@ Using high bit depth GIMP's "Colors/Exposure" to lighten the ground by one stop
 This step-by-step example provides a sample image and is broken down into five steps, starting with 
downloading the image. Steps 3, 4, and 5 describe the actual procedure, so here's an overview:
 
 <ol start='3' style='padding-left: 3rem; font-style: italic;' markdown=1 >
-
 3. Duplicate the base layer and then use GIMP's unbounded Levels to add one stop of positive exposure 
compensation to the duplicated layer.
 4. Add an inverse grayscale layer mask to the now much brighter duplicated layer.
 5. Do "Auto/Stretch Contrast" on the layer mask and then fine-tune the mask until you are happy. Then make a 
"New from Visible" layer.
-
 </ol>
 
 ---
 
 <ol style='max-width: 35rem;' markdown=1>
 
-<li><b>Download <a 
href="http://ninedegreesbelow.com/photography/gimp-tone-map-with-unbounded-rgb/tree.png";>tree.png</a></b>, 
which is a 16-bit integer sRGB image. High bit depth GIMP really is an "sRGB only" image editor, so it's best 
if you don't even try to edit in other RGB working spaces.</li>
+<li><b>Download <a href="tree.png">tree.png</a></b>, which is a 16-bit integer sRGB image. High bit depth 
GIMP really is an "sRGB only" image editor, so it's best if you don't even try to edit in other RGB working 
spaces.</li>
 
 <li><b>Open tree.png with GIMP and assign the GIMP built-in sRGB profile (the image colors won't change a 
bit). Then convert the image to 32-bit floating point linear precision</b>: Go to "Image/Precision", select 
"32-bit floating point", and when the Dither dialog pops up, select "Linear light" (this ensures that the 
Normal blend mode produces radiometrically correct results).</li>
 
 <li markdown=1> 
-Make a copy of the "tree.png" layer, and label it "+1 stop exposure comp". Then <b>use "Colors/Exposure" to 
add one stop of positive exposure compensation</b> — Figure 3 below shows the proper settings for the 
"Colors/Exposure" dialog, and Figure 4 shows the result:
+Make a copy of the "tree.png" layer, and label it "+1 stop exposure comp". Then <b>use "Colors/Exposure" to 
add one stop of positive exposure compensation</b>&mdash;Figure 3 below shows the proper settings for the 
"Colors/Exposure" dialog, and Figure 4 shows the result:
 
 <figure>
 <img src="gegl-exposure-add-one-stop-positive-exposure-compensation.jpg" 
alt="levels-add-one-stop-positive-exposure-compensation" >
@@ -113,7 +110,7 @@ When using "Colors/Exposure" to add one stop of positive exposure compensation,
 <li>
 <img style='float: right;' src="add-inverse-grayscale-mask.jpg" alt="add-inverse-grayscale-mask" >
 <b>Add an inverse grayscale layer mask</b>: Right-click on the layer and select "Layer/Mask/Add Layer Mask", 
and when the "Add a mask to the Layer" dialog pops up, choose "Grayscale copy of layer" and check the "Invert 
mask" box. 
-<p>As shown in Figure 5 below, at this point the highlights will be brought back into the display range, 
meaning all RGB channel values are between 0.0f and 1.0f. But the image will probably look a little odd (sort 
of cloudy and flat), and depending on the image, the brightest highlights might actually have dark splotches 
— don't worry! this is temporary.</p>
+<p>As shown in Figure 5 below, at this point the highlights will be brought back into the display range, 
meaning all RGB channel values are between 0.0f and 1.0f. But the image will probably look a little odd (sort 
of cloudy and flat), and depending on the image, the brightest highlights might actually have dark 
splotches&mdash;don't worry! this is temporary.</p>
  
 <figure >
 <img  src="gegl-exposure-inverse-grayscale-mask-added.jpg" alt="gegl-exposure-inverse-grayscale-mask-added" >
@@ -159,10 +156,19 @@ That's the whole procedure for using "Colors/Exposure" to add a stop of positive
 <figcaption>Using GIMP's floating point unbounded Levels plus layer masks to add two stops of positive 
exposure compensation to the shadows and midtones of a photograph of an apple orchard truck that was taken in 
bright sunshine.<br>
 (Click to view):<br>
 <span class='toggle-swap' data-fig-swap='apple-orchard-truck-from-camera.jpg'>1. Image from the camera, 
underexposed to avoid blowing out highlights..</span><br>
+<noscript>
+<img src='apple-orchard-truck-from-camera.jpg' alt='apple-orchard-truck-from-camera' 
style='margin-bottom:1rem;'>
+</noscript>
 <span class='toggle-swap' data-fig-swap='apple-orchard-truck-tone-mapped-using-gimp-colors-exposure.jpg'>2. 
After tone mapping/shadow recovery using high bit depth GIMP's floating point "Colors/Exposure".</span><br>
+<noscript>
+<img src='apple-orchard-truck-tone-mapped-using-gimp-colors-exposure.jpg' 
alt='apple-orchard-truck-tone-mapped-using-gimp-colors-exposure' style='margin-bottom:1rem;'>
+</noscript>
 <span class='toggle-swap' data-fig-swap='apple-orchard-truck-tone-mapped-using-gegl-mantuik.jpg'>3. For 
comparison, Mantuik tone-mapping using the GEGL default settings.</span><br>
+<noscript>
+<img src='apple-orchard-truck-tone-mapped-using-gegl-mantuik.jpg' 
alt='apple-orchard-truck-tone-mapped-using-gegl-mantuik' style='margin-bottom:1rem;'>
+</noscript>
 
-<p>Using GIMP's floating point floating point "Colors/Exposure" plus layer masks to add two and a half stops 
of positive exposure compensation to the shadows and midtones of a "bright sun" photograph of an apple 
orchard truck.</p>
+<p>Using GIMP's floating point "Colors/Exposure" plus layer masks to add two and a half stops of positive 
exposure compensation to the shadows and midtones of a "bright sun" photograph of an apple orchard truck.</p>
 
 <p><img style='float:right;' src="orchard-truck-layer-stack.jpg" alt="orchard-truck-layer-stack" >To the 
right is a screenshot of the layer stack that I used to tone-map the photograph of the apple orchard truck. 
Tone-mapping by hand gives you complete control over the resulting image. Mantuik and other "automagic" 
tone-mapping algorithms are CPU-intensive, unpredictable, and often produce unnatural-looking results.</p>
 </figcaption>
@@ -185,10 +191,19 @@ Before and after doing "Colors/Auto/Stretch Contrast" on the base layer, plus th
 
 <ol style='margin-top: 1rem;'>
 <li>This scene-referred interpolated raw file from the PhotoFlow raw processor (which provides a GIMP 
plug-in for easy opening of raw files) has out-of-display-range RGB channel values that will be brought back 
into the display range by doing "Colors/Auto/Stretch Contrast".</li>
+<noscript>
+<img src='before-auto-stretch-contrast.jpg' alt='before-auto-stretch-contrast' style='margin-top:-0.5rem; 
margin-bottom:1rem;'>
+</noscript>
 
 <li>After doing "Colors/Auto/Stretch Contrast", shadows are lighter and highlights are darker because the 
dynamic range has been compressed to fit within the display range. This looks like an editing step in the 
wrong direction! but actually it's necessary.</li>
+<noscript>
+<img src='after-auto-stretch-contrast.jpg' alt='after-auto-stretch-contrast' style='margin-top:-0.5rem; 
margin-bottom:1rem;'>
+</noscript>
 
 <li>Here's the final "Power lines" image after tone mapping the scene-referred interpolated raw file using 
the procedure described in this tutorial.</li>
+<noscript>
+<img src='power-lines.jpg' alt='power-lines' style='margin-top:-0.5rem; margin-bottom:1rem;'>
+</noscript>
 </ol>
 
 <p>As captured by the raw file, this picture of power lines marching into the distance is a typical result 
of taking a photograph at noon on a bright sunny day: The sky and clouds looked pretty good right out of the 
camera, but the ground was far too dark. So the image could benefit from some tone mapping to raise the 
shadows and midtones. The first step is to do "Colors/Auto/Stretch Contrast" to bring any channel values that 
are less than 0.0f or greater than 1.0f back within the display range of 0.0 to 1.0 floating point.</p> 
@@ -221,21 +236,31 @@ For the "Power lines" picture shown in Figure 8 above, after doing "Color/Auto/S
 
 
 <!-- pld -->
-<li id='blur-to-restore-micro-contrast'><b>Blurring the mask to restore micro contrast:</b> Putting an 
inverse mask on a layer that's used to add positive exposure compensation necessarily slightly flattens micro 
contrast. Depending on your artistic intentions for the image, you might want to blur the mask to restore 
micro contrast. The trick is how to blur the mask without introducing "halos" around the edges of objects in 
the image. Small radius gaussian blurs produce small but distressingly obvious halos around dark edges. A 
large radius gaussian blur sometimes works but just as often produces a large obvious halo separating the 
brighter and darker portions of the image. For many images a better solution is to blur the mask use an 
edge-respecting filter such as the GIMP <a href="https://github.com/dtschump/gmic";>G'MIC</a> bilateral smooth 
filter:
+<li id='blur-to-restore-micro-contrast'><b>Blurring the mask to restore micro contrast:</b> Putting an 
inverse mask on a layer that's used to add positive exposure compensation necessarily slightly flattens micro 
contrast. Depending on your artistic intentions for the image, you might want to blur the mask to restore 
micro contrast. The trick is how to blur the mask without introducing "halos" around the edges of objects in 
the image. Small radius Gaussian blurs produce small but distressingly obvious halos around dark edges. A 
large radius gaussian blur sometimes works but just as often produces a large obvious halo separating the 
brighter and darker portions of the image. For many images a better solution is to blur the mask use an 
edge-respecting filter such as the GIMP <a href="https://github.com/dtschump/gmic";>G'MIC</a> bilateral smooth 
filter:
 
 <figure>
 <img src='without-bilateral-smoothing-of-mask.jpg' alt='without-bilateral-smoothing-of-mask'>
 <figcaption>Adding exposure compensation with and without bilateral smoothing of the mask.<br>  
 (Click to view):<br>
 <span class='toggle-swap' data-fig-swap='without-bilateral-smoothing-of-mask.jpg'>Without applying bilateral 
smoothing to the mask, micro contrast is flattened.</span><br>
+
+<noscript>
+<img src='without-bilateral-smoothing-of-mask.jpg' alt='without-bilateral-smoothing-of-mask' 
style='margin-bottom: 1rem;'>
+</noscript>
+
 <span class='toggle-swap' data-fig-swap='with-bilateral-smoothing-of-mask.jpg'>After applying bilateral 
smoothing to the mask, micro contrast is restored.</span>
+
+<noscript>
+<img src='with-bilateral-smoothing-of-mask.jpg' alt='with-bilateral-smoothing-of-mask' style='margin-bottom: 
1rem;'>
+</noscript>
+
 <p>Adding exposure compensation combined with an inverse grayscale mask does flatten micro contrast, which 
might or might not be desireable depending on your artistic intentions for the image. To restore micro 
contrast, try using an edge-respecting blur such as G'MIC's bilateral smoothing filter. GIMP G'MIC doesn't 
work on layer masks. A workaround is to to turn the unblurred mask into a selection, save the selection as a 
channel, and then drag the channel to the layer stack for blurring.</p>
 </figcaption>
 </figure>
 </li>
 
 
-<li>An essential component of the procedure for using "Colors/Exposure" to add positive exposure 
compensation to images with dark shadows and midtones needs to be explicitly mentioned: Not only is the high 
bit depth GIMP's "Colors/Exposure" operation unbounded at floating point precision — <a title="GIMP bug 
report: Some filters / operations provide float values superior to 1.0." 
href="https://bugzilla.gnome.org/show_bug.cgi?id=737925";>layer masks are also unbounded</a>. 
+<li>An essential component of the procedure for using "Colors/Exposure" to add positive exposure 
compensation to images with dark shadows and midtones needs to be explicitly mentioned: Not only is the high 
bit depth GIMP's "Colors/Exposure" operation unbounded at floating point precision&mdash;<a title="GIMP bug 
report: Some filters / operations provide float values superior to 1.0." 
href="https://bugzilla.gnome.org/show_bug.cgi?id=737925";>layer masks are also unbounded</a>. 
 <p>If the inverted grayscale masks were summarily clipped (as is the case when editing at integer 
precision), then the procedure described in this tutorial wouldn't work.</p></li>
 
 </ol>
@@ -252,7 +277,9 @@ For the "Power lines" picture shown in Figure 8 above, after doing "Color/Auto/S
 
 <!-- END ARTICLE -->
 
-The original tutorial this was adapted from can be [found 
here](http://ninedegreesbelow.com/photography/gimp-tone-map-with-levels.html). (<http://ninedegreesbelow.com>)
+---
+
+The original tutorial this was adapted from can be [found 
here](http://ninedegreesbelow.com/photography/gimp-tone-map-with-levels.html) and is reproduced courtesy of 
Elle Stone (<http://ninedegreesbelow.com>).
 
 <small>
 <a href='http://creativecommons.org/licenses/by-sa/3.0/'>
diff --git a/content/tutorials/Tone_Mapping_Using_GIMP_Levels/tree.png 
b/content/tutorials/Tone_Mapping_Using_GIMP_Levels/tree.png
new file mode 100644
index 0000000..8326794
Binary files /dev/null and b/content/tutorials/Tone_Mapping_Using_GIMP_Levels/tree.png differ