Clean up and consolidate notes regarding the YUV image format. This also corrects a factual error regarding the padding of the luminance plane-- because we now support 4:1:1, the component width is not necessarily padded to the nearest multiple of 2 if horizontal subsampling is used.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1342 632fc199-4ca6-4c93-a231-07263d6284db
This commit is contained in:
DRC
@@ -857,7 +857,7 @@
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<dd> </dd>
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<dt><a href="./org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg"><span class="strong">YUVImage</span></a> - Class in <a href="./org/libjpegturbo/turbojpeg/package-summary.html">org.libjpegturbo.turbojpeg</a></dt>
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<dd>
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<div class="block">This class encapsulates a YUV planar image buffer and the metadata
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<div class="block">This class encapsulates a YUV planar image and the metadata
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associated with it.</div>
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</dd>
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<dt><span class="strong"><a href="./org/libjpegturbo/turbojpeg/YUVImage.html#YUVImage(int, int, int, int)">YUVImage(int, int, int, int)</a></span> - Constructor for class org.libjpegturbo.turbojpeg.<a href="./org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg">YUVImage</a></dt>
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@@ -94,7 +94,7 @@
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<br>
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<pre>public class <span class="strong">YUVImage</span>
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extends java.lang.Object</pre>
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<div class="block">This class encapsulates a YUV planar image buffer and the metadata
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<div class="block">This class encapsulates a YUV planar image and the metadata
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associated with it. The TurboJPEG API allows both the JPEG compression and
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decompression pipelines to be split into stages: YUV encode, compress from
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YUV, decompress to YUV, and YUV decode. A <code>YUVImage</code> instance
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@@ -105,18 +105,28 @@ extends java.lang.Object</pre>
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Technically, the JPEG format uses the YCbCr colorspace (which technically is
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not a "colorspace" but rather a "color transform"), but per the convention
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of the digital video community, the TurboJPEG API uses "YUV" to refer to an
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image format consisting of Y, Cb, and Cr image planes. In this image
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format, the Y, Cb (U), and Cr (V) planes are stored sequentially in the same
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image buffer, and the size of each plane is determined by the image width,
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height, line padding, and level of chrominance subsampling. If the
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chrominance components are subsampled along the horizontal dimension, then
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the width of the luminance plane would be padded to the nearest multiple of
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2 (same goes for the height of the luminance plane, if the chrominance
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components are subsampled along the vertical dimension.) For instance, if
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the source image is 35 x 35 pixels and 4:2:2 subsampling is used, then the
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luminance plane would be 36 x 35 bytes, and each of the chrominance planes
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would be 18 x 35 bytes. If you specify, for instance, a line padding of 4
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bytes on top of this, then the luminance plane would be 36 x 35 bytes, and
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image format consisting of Y, Cb, and Cr image planes.
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<p>
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Each plane is simply a 2D array of bytes, each byte representing the value
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of one of the components at a particular location in the image. The
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"component width" and "component height" of each plane are determined by the
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image width, height, and level of chrominance subsampling. For the
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luminance plane, the component width is the image width padded to the
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nearest multiple of the horizontal subsampling factor (2 in the case of
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4:2:0 and 4:2:2, 4 in the case of 4:1:1, 1 in the case of 4:4:4 or
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grayscale.) Similarly, the component height of the luminance plane is the
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image height padded to the nearest multiple of the vertical subsampling
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factor (2 in the case of 4:2:0 or 4:4:0, 1 in the case of 4:4:4 or
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grayscale.) The component width of the chrominance planes is equal to the
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component width of the luminance plane divided by the horizontal subsampling
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factor, and the component height of the chrominance planes is equal to the
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component height of the luminance plane divided by the vertical subsampling
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factor.
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<p>
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For example, if the source image is 35 x 35 pixels and 4:2:2 subsampling is
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used, then the luminance plane would be 36 x 35 bytes, and each of the
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chrominance planes would be 18 x 35 bytes. If you specify a line padding of
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4 bytes on top of this, then the luminance plane would be 36 x 35 bytes, and
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each of the chrominance planes would be 20 x 35 bytes.</div>
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</li>
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</ul>
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@@ -372,9 +382,10 @@ extends java.lang.Object</pre>
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<div class="block">Create a <code>YUVImage</code> instance from an existing YUV planar image
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buffer.</div>
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<dl><dt><span class="strong">Parameters:</span></dt><dd><code>yuvImage</code> - image buffer that contains or will contain YUV planar
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image data. See <a href="../../../org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg"><code>above</code></a> for a description of the image
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format. Use <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#bufSizeYUV(int, int, int, int)"><code>TJ.bufSizeYUV(int, int, int, int)</code></a> to determine the minimum size for this
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buffer.</dd><dd><code>width</code> - width (in pixels) of the YUV image</dd><dd><code>pad</code> - the line padding used in the YUV image buffer. For
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image data. Use <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#bufSizeYUV(int, int, int, int)"><code>TJ.bufSizeYUV(int, int, int, int)</code></a> to determine the minimum size for
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this buffer. The Y, U (Cb), and V (Cr) image planes are stored
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sequentially in the buffer (see <a href="../../../org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg"><code>above</code></a> for a description
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of the image format.)</dd><dd><code>width</code> - width (in pixels) of the YUV image</dd><dd><code>pad</code> - the line padding used in the YUV image buffer. For
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instance, if each line in each plane of the buffer is padded to the
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nearest multiple of 4 bytes, then <code>pad</code> should be set to 4.</dd><dd><code>height</code> - height (in pixels) of the YUV image</dd><dd><code>subsamp</code> - the level of chrominance subsampling used in the YUV
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image (one of <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#SAMP_444"><code>TJ.SAMP_*</code></a>)</dd>
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@@ -405,9 +416,10 @@ extends java.lang.Object</pre>
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<div class="block">Assign an existing YUV planar image buffer to this <code>YUVImage</code>
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instance.</div>
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<dl><dt><span class="strong">Parameters:</span></dt><dd><code>yuvImage</code> - image buffer that contains or will contain YUV planar
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image data. See <a href="../../../org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg"><code>above</code></a> for a description of the image
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format. Use <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#bufSizeYUV(int, int, int, int)"><code>TJ.bufSizeYUV(int, int, int, int)</code></a> to determine the minimum size for this
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buffer.</dd><dd><code>width</code> - width (in pixels) of the YUV image</dd><dd><code>pad</code> - the line padding used in the YUV image buffer. For
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image data. Use <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#bufSizeYUV(int, int, int, int)"><code>TJ.bufSizeYUV(int, int, int, int)</code></a> to determine the minimum size for
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this buffer. The Y, U (Cb), and V (Cr) image planes are stored
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sequentially in the buffer (see <a href="../../../org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg"><code>above</code></a> for a description
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of the image format.)</dd><dd><code>width</code> - width (in pixels) of the YUV image</dd><dd><code>pad</code> - the line padding used in the YUV image buffer. For
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instance, if each line in each plane of the buffer is padded to the
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nearest multiple of 4 bytes, then <code>pad</code> should be set to 4.</dd><dd><code>height</code> - height (in pixels) of the YUV image</dd><dd><code>subsamp</code> - the level of chrominance subsampling used in the YUV
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image (one of <a href="../../../org/libjpegturbo/turbojpeg/TJ.html#SAMP_444"><code>TJ.SAMP_*</code></a>)</dd>
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@@ -127,7 +127,7 @@
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<tr class="altColor">
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<td class="colFirst"><a href="../../../org/libjpegturbo/turbojpeg/YUVImage.html" title="class in org.libjpegturbo.turbojpeg">YUVImage</a></td>
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<td class="colLast">
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<div class="block">This class encapsulates a YUV planar image buffer and the metadata
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<div class="block">This class encapsulates a YUV planar image and the metadata
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associated with it.</div>
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</td>
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</tr>
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@@ -29,7 +29,7 @@
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package org.libjpegturbo.turbojpeg;
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/**
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* This class encapsulates a YUV planar image buffer and the metadata
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* This class encapsulates a YUV planar image and the metadata
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* associated with it. The TurboJPEG API allows both the JPEG compression and
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* decompression pipelines to be split into stages: YUV encode, compress from
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* YUV, decompress to YUV, and YUV decode. A <code>YUVImage</code> instance
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@@ -40,18 +40,28 @@ package org.libjpegturbo.turbojpeg;
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* Technically, the JPEG format uses the YCbCr colorspace (which technically is
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* not a "colorspace" but rather a "color transform"), but per the convention
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* of the digital video community, the TurboJPEG API uses "YUV" to refer to an
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* image format consisting of Y, Cb, and Cr image planes. In this image
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* format, the Y, Cb (U), and Cr (V) planes are stored sequentially in the same
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* image buffer, and the size of each plane is determined by the image width,
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* height, line padding, and level of chrominance subsampling. If the
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* chrominance components are subsampled along the horizontal dimension, then
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* the width of the luminance plane would be padded to the nearest multiple of
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* 2 (same goes for the height of the luminance plane, if the chrominance
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* components are subsampled along the vertical dimension.) For instance, if
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* the source image is 35 x 35 pixels and 4:2:2 subsampling is used, then the
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* luminance plane would be 36 x 35 bytes, and each of the chrominance planes
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* would be 18 x 35 bytes. If you specify, for instance, a line padding of 4
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* bytes on top of this, then the luminance plane would be 36 x 35 bytes, and
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* image format consisting of Y, Cb, and Cr image planes.
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* <p>
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* Each plane is simply a 2D array of bytes, each byte representing the value
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* of one of the components at a particular location in the image. The
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* "component width" and "component height" of each plane are determined by the
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* image width, height, and level of chrominance subsampling. For the
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* luminance plane, the component width is the image width padded to the
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* nearest multiple of the horizontal subsampling factor (2 in the case of
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* 4:2:0 and 4:2:2, 4 in the case of 4:1:1, 1 in the case of 4:4:4 or
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* grayscale.) Similarly, the component height of the luminance plane is the
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* image height padded to the nearest multiple of the vertical subsampling
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* factor (2 in the case of 4:2:0 or 4:4:0, 1 in the case of 4:4:4 or
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* grayscale.) The component width of the chrominance planes is equal to the
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* component width of the luminance plane divided by the horizontal subsampling
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* factor, and the component height of the chrominance planes is equal to the
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* component height of the luminance plane divided by the vertical subsampling
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* factor.
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* <p>
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* For example, if the source image is 35 x 35 pixels and 4:2:2 subsampling is
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* used, then the luminance plane would be 36 x 35 bytes, and each of the
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* chrominance planes would be 18 x 35 bytes. If you specify a line padding of
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* 4 bytes on top of this, then the luminance plane would be 36 x 35 bytes, and
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* each of the chrominance planes would be 20 x 35 bytes.
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*/
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public class YUVImage {
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@@ -83,9 +93,10 @@ public class YUVImage {
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* buffer.
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*
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* @param yuvImage image buffer that contains or will contain YUV planar
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* image data. See {@link YUVImage above} for a description of the image
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* format. Use {@link TJ#bufSizeYUV} to determine the minimum size for this
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* buffer.
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* image data. Use {@link TJ#bufSizeYUV} to determine the minimum size for
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* this buffer. The Y, U (Cb), and V (Cr) image planes are stored
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* sequentially in the buffer (see {@link YUVImage above} for a description
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* of the image format.)
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*
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* @param width width (in pixels) of the YUV image
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*
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@@ -108,9 +119,10 @@ public class YUVImage {
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* instance.
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*
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* @param yuvImage image buffer that contains or will contain YUV planar
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* image data. See {@link YUVImage above} for a description of the image
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* format. Use {@link TJ#bufSizeYUV} to determine the minimum size for this
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* buffer.
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* image data. Use {@link TJ#bufSizeYUV} to determine the minimum size for
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* this buffer. The Y, U (Cb), and V (Cr) image planes are stored
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* sequentially in the buffer (see {@link YUVImage above} for a description
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* of the image format.)
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*
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* @param width width (in pixels) of the YUV image
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*
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