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video: add method to get offset and scale for a format

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Add a method to get the offset and scale values to transform the color values of
a format to their normalized [0.0 .. 1.0] range. This is usually required as
the first step of a colorspace conversion.
This commit is contained in:
Wim Taymans 2012-07-13 17:13:10 +02:00
parent a18c098f82
commit eacb9ee554
2 changed files with 73 additions and 0 deletions
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64
gst-libs/gst/video/video-color.c
View file

@ -152,6 +152,70 @@ gst_video_colorimetry_matches (GstVideoColorimetry * cinfo, const gchar * color)
return FALSE;
}
/**
* gst_video_color_range_offsets:
* @range: a #GstVideoColorRange
* @info: a #GstVideoFormatInfo
* @offsets: (out): output offsets
* @scale: (out): output scale
*
* Compute the offset and scale values for each component of @info. For each
* component, (c[i] - offset[i]) / scale[i] will scale the component c[i] to the
* range [0.0 .. 1.0].
*
* The reverse operation (c[i] * scale[i]) + offset[i] can be used to convert
* the component values in range [0.0 .. 1.0] back to their representation in
* @info and @range.
*/
void
gst_video_color_range_offsets (GstVideoColorRange range,
const GstVideoFormatInfo * info, gint offset[GST_VIDEO_MAX_COMPONENTS],
gint scale[GST_VIDEO_MAX_COMPONENTS])
{
gboolean yuv;
yuv = GST_VIDEO_FORMAT_INFO_IS_YUV (info);
switch (range) {
default:
case GST_VIDEO_COLOR_RANGE_0_255:
offset[0] = 0;
if (yuv) {
offset[1] = 1 << (info->depth[1] - 1);
offset[2] = 1 << (info->depth[2] - 1);
} else {
offset[1] = 0;
offset[2] = 0;
}
scale[0] = (1 << info->depth[0]) - 1;
scale[1] = (1 << info->depth[1]) - 1;
scale[2] = (1 << info->depth[2]) - 1;
break;
case GST_VIDEO_COLOR_RANGE_16_235:
offset[0] = 1 << (info->depth[0] - 4);
scale[0] = 219 << (info->depth[0] - 8);
if (yuv) {
offset[1] = 1 << (info->depth[1] - 1);
offset[2] = 1 << (info->depth[2] - 1);
scale[1] = 224 << (info->depth[1] - 8);
scale[2] = 224 << (info->depth[2] - 8);
} else {
offset[1] = 1 << (info->depth[1] - 4);
offset[2] = 1 << (info->depth[2] - 4);
scale[1] = 219 << (info->depth[1] - 8);
scale[2] = 219 << (info->depth[2] - 8);
}
break;
}
/* alpha channel is always full range */
offset[3] = 0;
scale[3] = (1 << info->depth[3]) - 1;
GST_DEBUG ("scale: %d %d %d %d", scale[0], scale[1], scale[2], scale[3]);
GST_DEBUG ("offset: %d %d %d %d", offset[0], offset[1], offset[2], offset[3]);
}
#if 0
typedef struct
{

9
gst-libs/gst/video/video-color.h
View file

@ -22,6 +22,8 @@
#include <gst/gst.h>
#include <gst/video/video-format.h>
G_BEGIN_DECLS
/**
@ -147,6 +149,13 @@ gboolean gst_video_colorimetry_matches (GstVideoColorimetry *cinfo, cons
gboolean gst_video_colorimetry_from_string (GstVideoColorimetry *cinfo, const gchar *color);
gchar * gst_video_colorimetry_to_string (GstVideoColorimetry *cinfo);
/* compute offset and scale */
void gst_video_color_range_offsets (GstVideoColorRange range,
const GstVideoFormatInfo *info,
gint offset[GST_VIDEO_MAX_COMPONENTS],
gint scale[GST_VIDEO_MAX_COMPONENTS]);
G_END_DECLS
#endif /* __GST_VIDEO_COLOR_H__ */