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swscale: Add Doxygen for hyscale_fast/hScale.

This commit is contained in:
Ronald S. Bultje 2011-06-28 21:32:40 +02:00 committed by Diego Biurrun
parent b0da4903dd
commit 4578435f35
1 changed files with 45 additions and 0 deletions
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45
libswscale/swscale_internal.h
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@ -386,6 +386,25 @@ typedef struct SwsContext {
void (*chrToYV12)(uint8_t *dstU, uint8_t *dstV,
const uint8_t *src1, const uint8_t *src2,
int width, uint32_t *pal); ///< Unscaled conversion of chroma planes to YV12 for horizontal scaler.
/**
* Scale one horizontal line of input data using a bilinear filter
* to produce one line of output data. Compared to SwsContext->hScale(),
* please take note of the following caveats when using these:
* - Scaling is done using only 7bit instead of 14bit coefficients.
* - You can use no more than 5 input pixels to produce 4 output
* pixels. Therefore, this filter should not be used for downscaling
* by more than ~20% in width (because that equals more than 5/4th
* downscaling and thus more than 5 pixels input per 4 pixels output).
* - In general, bilinear filters create artifacts during downscaling
* (even when <20%), because one output pixel will span more than one
* input pixel, and thus some pixels will need edges of both neighbor
* pixels to interpolate the output pixel. Since you can use at most
* two input pixels per output pixel in bilinear scaling, this is
* impossible and thus downscaling by any size will create artifacts.
* To enable this type of scaling, set SWS_FLAG_FAST_BILINEAR
* in SwsContext->flags.
*/
/** @{ */
void (*hyscale_fast)(struct SwsContext *c,
int16_t *dst, int dstWidth,
const uint8_t *src, int srcW, int xInc);
@ -393,7 +412,33 @@ typedef struct SwsContext {
int16_t *dst1, int16_t *dst2, int dstWidth,
const uint8_t *src1, const uint8_t *src2,
int srcW, int xInc);
/** @} */
/**
* Scale one horizontal line of input data using a filter over the input
* lines, to produce one (differently sized) line of output data.
*
* @param dst pointer to destination buffer for horizontally scaled
* data. If the scaling depth (SwsContext->scalingBpp) is
* 8, data will be 15bpp in 16bits (int16_t) width. If
* scaling depth is 16, data will be 19bpp in 32bpp
* (int32_t) width.
* @param dstW width of destination image
* @param src pointer to source data to be scaled. If scaling depth
* is 8, this is 8bpp in 8bpp (uint8_t) width. If scaling
* depth is 16, this is 16bpp in 16bpp (uint16_t) depth.
* @param filter filter coefficients to be used per output pixel for
* scaling. This contains 14bpp filtering coefficients.
* Guaranteed to contain dstW * filterSize entries.
* @param filterPos position of the first input pixel to be used for
* each output pixel during scaling. Guaranteed to
* contain dstW entries.
* @param filterSize the number of input coefficients to be used (and
* thus the number of input pixels to be used) for
* creating a single output pixel. Is aligned to 4
* (and input coefficients thus padded with zeroes)
* to simplify creating SIMD code.
*/
void (*hScale)(int16_t *dst, int dstW, const uint8_t *src,
const int16_t *filter, const int16_t *filterPos,
int filterSize);