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TJ doc: Density params require YCbCr or grayscale

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Since libjpeg-turbo does not support Exif, the only way it can embed
density information in a JPEG image is by using the JFIF marker, which
is only written if the JPEG colorspace is YCbCr or grayscale.
(Referring to the conversation under #793, we may need to further
restrict that to 8-bit-per-sample JPEG images, because the JFIF spec
requires 8-bit data precision.)
This commit is contained in:
DRC
2024-10-30 12:12:03 -04:00
parent 45fa88190f
commit 3be781679c
7 changed files with 33 additions and 3 deletions
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3
doc/html/group___turbo_j_p_e_g.html
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@@ -992,6 +992,7 @@ scalingFactor)</code>. </p>
<li>The JPEG image has (decompression) or will have (compression) the specified horizontal pixel density <em>[default for compression: <code>1</code>]</em>.</li>
</ul>
<p>This value is stored in or read from the JPEG header. It does not affect the contents of the JPEG image. Note that this parameter is set by <a class="el" href="group___turbo_j_p_e_g.html#ga884023536e70985616126a073f662001" title="Load an 8-bit-per-sample packed-pixel image from disk into memory.">tj3LoadImage8()</a> when loading a Windows BMP file that contains pixel density information, and the value of this parameter is stored to a Windows BMP file by <a class="el" href="group___turbo_j_p_e_g.html#gaa4ec838988e469cc15618e4690cc8722" title="Save an 8-bit-per-sample packed-pixel image from memory to disk.">tj3SaveImage8()</a> if the value of <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208" title="JPEG pixel density units.">TJPARAM_DENSITYUNITS</a> is <code>2</code>.</p>
<p>This parameter has no effect unless the JPEG colorspace (see <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a46a10d46309514907d0c39fcd86c324c" title="JPEG colorspace.">TJPARAM_COLORSPACE</a>) is <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720a7389b8f65bb387ffedce3efd0d78ec75" title="YCbCr colorspace.">TJCS_YCbCr</a> or <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720ab3e7d6a87f695e45b81c1b5262b5a50a" title="Grayscale colorspace.">TJCS_GRAY</a>.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208" title="JPEG pixel density units.">TJPARAM_DENSITYUNITS</a> </dd></dl>
</td></tr>
<tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82abda48f2df7eb9b88e2b7621efb017eba" name="ggaa0f6be63ba78278299c9f5c12031fe82abda48f2df7eb9b88e2b7621efb017eba"></a>TJPARAM_YDENSITY&#160;</td><td class="fielddoc"><p>JPEG vertical pixel density. </p>
@@ -999,6 +1000,7 @@ scalingFactor)</code>. </p>
<li>The JPEG image has (decompression) or will have (compression) the specified vertical pixel density <em>[default for compression: <code>1</code>]</em>.</li>
</ul>
<p>This value is stored in or read from the JPEG header. It does not affect the contents of the JPEG image. Note that this parameter is set by <a class="el" href="group___turbo_j_p_e_g.html#ga884023536e70985616126a073f662001" title="Load an 8-bit-per-sample packed-pixel image from disk into memory.">tj3LoadImage8()</a> when loading a Windows BMP file that contains pixel density information, and the value of this parameter is stored to a Windows BMP file by <a class="el" href="group___turbo_j_p_e_g.html#gaa4ec838988e469cc15618e4690cc8722" title="Save an 8-bit-per-sample packed-pixel image from memory to disk.">tj3SaveImage8()</a> if the value of <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208" title="JPEG pixel density units.">TJPARAM_DENSITYUNITS</a> is <code>2</code>.</p>
<p>This parameter has no effect unless the JPEG colorspace (see <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a46a10d46309514907d0c39fcd86c324c" title="JPEG colorspace.">TJPARAM_COLORSPACE</a>) is <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720a7389b8f65bb387ffedce3efd0d78ec75" title="YCbCr colorspace.">TJCS_YCbCr</a> or <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720ab3e7d6a87f695e45b81c1b5262b5a50a" title="Grayscale colorspace.">TJCS_GRAY</a>.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208" title="JPEG pixel density units.">TJPARAM_DENSITYUNITS</a> </dd></dl>
</td></tr>
<tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208" name="ggaa0f6be63ba78278299c9f5c12031fe82a4c045981bd8a303521a401dbbe1df208"></a>TJPARAM_DENSITYUNITS&#160;</td><td class="fielddoc"><p>JPEG pixel density units. </p>
@@ -1008,6 +1010,7 @@ scalingFactor)</code>. </p>
<li><code>2</code> The pixel density of the JPEG image is expressed (decompression) or will be expressed (compression) in units of pixels/cm.</li>
</ul>
<p>This value is stored in or read from the JPEG header. It does not affect the contents of the JPEG image. Note that this parameter is set by <a class="el" href="group___turbo_j_p_e_g.html#ga884023536e70985616126a073f662001" title="Load an 8-bit-per-sample packed-pixel image from disk into memory.">tj3LoadImage8()</a> when loading a Windows BMP file that contains pixel density information, and the value of this parameter is stored to a Windows BMP file by <a class="el" href="group___turbo_j_p_e_g.html#gaa4ec838988e469cc15618e4690cc8722" title="Save an 8-bit-per-sample packed-pixel image from memory to disk.">tj3SaveImage8()</a> if the value is <code>2</code>.</p>
<p>This parameter has no effect unless the JPEG colorspace (see <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a46a10d46309514907d0c39fcd86c324c" title="JPEG colorspace.">TJPARAM_COLORSPACE</a>) is <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720a7389b8f65bb387ffedce3efd0d78ec75" title="YCbCr colorspace.">TJCS_YCbCr</a> or <a class="el" href="group___turbo_j_p_e_g.html#gga4f83ad3368e0e29d1957be0efa7c3720ab3e7d6a87f695e45b81c1b5262b5a50a" title="Grayscale colorspace.">TJCS_GRAY</a>.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82a4de5c9d7cab5be806143a43c3b0e0877" title="JPEG horizontal pixel density.">TJPARAM_XDENSITY</a>, <a class="el" href="group___turbo_j_p_e_g.html#ggaa0f6be63ba78278299c9f5c12031fe82abda48f2df7eb9b88e2b7621efb017eba" title="JPEG vertical pixel density.">TJPARAM_YDENSITY</a> </dd></dl>
</td></tr>
<tr><td class="fieldname"><a id="ggaa0f6be63ba78278299c9f5c12031fe82a0de0a8281da45d1fc984edc8918f7dd2" name="ggaa0f6be63ba78278299c9f5c12031fe82a0de0a8281da45d1fc984edc8918f7dd2"></a>TJPARAM_MAXMEMORY&#160;</td><td class="fielddoc"><p>Memory limit for intermediate buffers. </p>

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@@ -1878,7 +1878,10 @@ extends java.lang.Object</pre>
</ul>
<p>This value is stored in or read from the JPEG header. It does not
affect the contents of the JPEG image.</div>
affect the contents of the JPEG image.
<p>This parameter has no effect unless the JPEG colorspace (see
<a href="#PARAM_COLORSPACE"><code>PARAM_COLORSPACE</code></a>) is <a href="#CS_YCbCr"><code>CS_YCbCr</code></a> or <a href="#CS_GRAY"><code>CS_GRAY</code></a>.</div>
<dl>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="#PARAM_DENSITYUNITS"><code>PARAM_DENSITYUNITS</code></a>,
@@ -1903,7 +1906,10 @@ extends java.lang.Object</pre>
</ul>
<p>This value is stored in or read from the JPEG header. It does not
affect the contents of the JPEG image.</div>
affect the contents of the JPEG image.
<p>This parameter has no effect unless the JPEG colorspace (see
<a href="#PARAM_COLORSPACE"><code>PARAM_COLORSPACE</code></a>) is <a href="#CS_YCbCr"><code>CS_YCbCr</code></a> or <a href="#CS_GRAY"><code>CS_GRAY</code></a>.</div>
<dl>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="#PARAM_DENSITYUNITS"><code>PARAM_DENSITYUNITS</code></a>,
@@ -1933,7 +1939,10 @@ extends java.lang.Object</pre>
</ul>
<p>This value is stored in or read from the JPEG header. It does not
affect the contents of the JPEG image.</div>
affect the contents of the JPEG image.
<p>This parameter has no effect unless the JPEG colorspace (see
<a href="#PARAM_COLORSPACE"><code>PARAM_COLORSPACE</code></a>) is <a href="#CS_YCbCr"><code>CS_YCbCr</code></a> or <a href="#CS_GRAY"><code>CS_GRAY</code></a>.</div>
<dl>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="#PARAM_XDENSITY"><code>PARAM_XDENSITY</code></a>,

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java/org/libjpegturbo/turbojpeg/TJ.java
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@@ -851,6 +851,9 @@ public final class TJ {
* <p>This value is stored in or read from the JPEG header. It does not
* affect the contents of the JPEG image.
*
* <p>This parameter has no effect unless the JPEG colorspace (see
* {@link #PARAM_COLORSPACE}) is {@link #CS_YCbCr} or {@link #CS_GRAY}.
*
* @see #PARAM_DENSITYUNITS
*/
public static final int PARAM_XDENSITY = 20;
@@ -867,6 +870,9 @@ public final class TJ {
* <p>This value is stored in or read from the JPEG header. It does not
* affect the contents of the JPEG image.
*
* <p>This parameter has no effect unless the JPEG colorspace (see
* {@link #PARAM_COLORSPACE}) is {@link #CS_YCbCr} or {@link #CS_GRAY}.
*
* @see #PARAM_DENSITYUNITS
*/
public static final int PARAM_YDENSITY = 21;
@@ -888,6 +894,9 @@ public final class TJ {
* <p>This value is stored in or read from the JPEG header. It does not
* affect the contents of the JPEG image.
*
* <p>This parameter has no effect unless the JPEG colorspace (see
* {@link #PARAM_COLORSPACE}) is {@link #CS_YCbCr} or {@link #CS_GRAY}.
*
* @see #PARAM_XDENSITY
* @see #PARAM_YDENSITY
*/

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turbojpeg.h
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@@ -836,6 +836,9 @@ enum TJPARAM {
* Windows BMP file by #tj3SaveImage8() if the value of #TJPARAM_DENSITYUNITS
* is `2`.
*
* This parameter has no effect unless the JPEG colorspace (see
* #TJPARAM_COLORSPACE) is #TJCS_YCbCr or #TJCS_GRAY.
*
* @see TJPARAM_DENSITYUNITS
*/
TJPARAM_XDENSITY,
@@ -853,6 +856,9 @@ enum TJPARAM {
* Windows BMP file by #tj3SaveImage8() if the value of #TJPARAM_DENSITYUNITS
* is `2`.
*
* This parameter has no effect unless the JPEG colorspace (see
* #TJPARAM_COLORSPACE) is #TJCS_YCbCr or #TJCS_GRAY.
*
* @see TJPARAM_DENSITYUNITS
*/
TJPARAM_YDENSITY,
@@ -874,6 +880,9 @@ enum TJPARAM {
* density information, and the value of this parameter is stored to a
* Windows BMP file by #tj3SaveImage8() if the value is `2`.
*
* This parameter has no effect unless the JPEG colorspace (see
* #TJPARAM_COLORSPACE) is #TJCS_YCbCr or #TJCS_GRAY.
*
* @see TJPARAM_XDENSITY, TJPARAM_YDENSITY
*/
TJPARAM_DENSITYUNITS,