pixdesc.h 6.46 KB
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/*
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 * pixel format descriptor
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 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

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#ifndef AVUTIL_PIXDESC_H
#define AVUTIL_PIXDESC_H
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#include <inttypes.h>

typedef struct AVComponentDescriptor{
    uint16_t plane        :2;            ///< which of the 4 planes contains the component
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    /**
     * Number of elements between 2 horizontally consecutive pixels minus 1.
     * Elements are bits for bitstream formats, bytes otherwise.
     */
    uint16_t step_minus1  :3;

    /**
     * Number of elements before the component of the first pixel plus 1.
     * Elements are bits for bitstream formats, bytes otherwise.
     */
    uint16_t offset_plus1 :3;
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    uint16_t shift        :3;            ///< number of least significant bits that must be shifted away to get the value
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    uint16_t depth_minus1 :4;            ///< number of bits in the component minus 1
}AVComponentDescriptor;

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/**
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 * Descriptor that unambiguously describes how the bits of a pixel are
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 * stored in the up to 4 data planes of an image. It also stores the
 * subsampling factors and number of components.
 *
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 * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
 *       and all the YUV variants) AVPixFmtDescriptor just stores how values
 *       are stored not what these values represent.
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 */
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typedef struct AVPixFmtDescriptor{
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    const char *name;
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    uint8_t nb_components;      ///< The number of components each pixel has, (1-4)
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    /**
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     * Amount to shift the luma width right to find the chroma width.
     * For YV12 this is 1 for example.
     * chroma_width = -((-luma_width) >> log2_chroma_w)
     * The note above is needed to ensure rounding up.
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     * This value only refers to the chroma components.
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     */
    uint8_t log2_chroma_w;      ///< chroma_width = -((-luma_width )>>log2_chroma_w)

    /**
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     * Amount to shift the luma height right to find the chroma height.
     * For YV12 this is 1 for example.
     * chroma_height= -((-luma_height) >> log2_chroma_h)
     * The note above is needed to ensure rounding up.
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     * This value only refers to the chroma components.
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     */
    uint8_t log2_chroma_h;
    uint8_t flags;
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    /**
     * Parameters that describe how pixels are packed. If the format
     * has chroma components, they must be stored in comp[1] and
     * comp[2].
     */
    AVComponentDescriptor comp[4];
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}AVPixFmtDescriptor;

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#define PIX_FMT_BE        1 ///< Pixel format is big-endian.
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#define PIX_FMT_PAL       2 ///< Pixel format has a palette in data[1], values are indexes in this palette.
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#define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.
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#define PIX_FMT_HWACCEL   8 ///< Pixel format is an HW accelerated format.
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/**
 * The array of all the pixel format descriptors.
 */
extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
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/**
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 * Read a line from an image, and write the values of the
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 * pixel format component c to dst.
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 *
 * @param data the array containing the pointers to the planes of the image
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 * @param linesize the array containing the linesizes of the image
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 * @param desc the pixel format descriptor for the image
 * @param x the horizontal coordinate of the first pixel to read
 * @param y the vertical coordinate of the first pixel to read
 * @param w the width of the line to read, that is the number of
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 * values to write to dst
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 * @param read_pal_component if not zero and the format is a paletted
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 * format writes the values corresponding to the palette
 * component c in data[1] to dst, rather than the palette indexes in
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 * data[0]. The behavior is undefined if the format is not paletted.
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 */
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void av_read_image_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4],
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                        const AVPixFmtDescriptor *desc, int x, int y, int c, int w, int read_pal_component);
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/**
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 * Write the values from src to the pixel format component c of an
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 * image line.
 *
 * @param src array containing the values to write
 * @param data the array containing the pointers to the planes of the
 * image to write into. It is supposed to be zeroed.
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 * @param linesize the array containing the linesizes of the image
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 * @param desc the pixel format descriptor for the image
 * @param x the horizontal coordinate of the first pixel to write
 * @param y the vertical coordinate of the first pixel to write
 * @param w the width of the line to write, that is the number of
 * values to write to the image line
 */
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void av_write_image_line(const uint16_t *src, uint8_t *data[4], const int linesize[4],
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                         const AVPixFmtDescriptor *desc, int x, int y, int c, int w);
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/**
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 * Return the pixel format corresponding to name.
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 *
 * If there is no pixel format with name name, then looks for a
 * pixel format with the name corresponding to the native endian
 * format of name.
 * For example in a little-endian system, first looks for "gray16",
 * then for "gray16le".
 *
 * Finally if no pixel format has been found, returns PIX_FMT_NONE.
 */
enum PixelFormat av_get_pix_fmt(const char *name);

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/**
 * Print in buf the string corresponding to the pixel format with
 * number pix_fmt, or an header if pix_fmt is negative.
 *
 * @param buf the buffer where to write the string
 * @param buf_size the size of buf
 * @param pix_fmt the number of the pixel format to print the
 * corresponding info string, or a negative value to print the
 * corresponding header.
 */
char *av_get_pix_fmt_string (char *buf, int buf_size, enum PixelFormat pix_fmt);

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/**
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 * Return the number of bits per pixel used by the pixel format
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 * described by pixdesc.
 *
 * The returned number of bits refers to the number of bits actually
 * used for storing the pixel information, that is padding bits are
 * not counted.
 */
int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);

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#endif /* AVUTIL_PIXDESC_H */