79 lines
3.0 KiB
C
79 lines
3.0 KiB
C
// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Rescaling functions
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#ifndef WEBP_UTILS_RESCALER_H_
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#define WEBP_UTILS_RESCALER_H_
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#include "../webp/types.h"
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// Structure used for on-the-fly rescaling
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typedef struct {
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int x_expand; // true if we're expanding in the x direction
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int num_channels; // bytes to jump between pixels
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int fy_scale, fx_scale; // fixed-point scaling factor
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int64_t fxy_scale; // ''
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// we need hpel-precise add/sub increments, for the downsampled U/V planes.
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int y_accum; // vertical accumulator
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int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst)
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int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst)
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int src_width, src_height; // source dimensions
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int dst_width, dst_height; // destination dimensions
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uint8_t* dst;
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int dst_stride;
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int32_t* irow, *frow; // work buffer
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} WebPRescaler;
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// Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
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void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
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uint8_t* const dst,
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int dst_width, int dst_height, int dst_stride,
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int num_channels,
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int x_add, int x_sub,
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int y_add, int y_sub,
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int32_t* const work);
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// Import a row of data and save its contribution in the rescaler.
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// 'channel' denotes the channel number to be imported.
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void WebPRescalerImportRow(WebPRescaler* const rescaler,
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const uint8_t* const src, int channel);
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// Import multiple rows over all channels, until at least one row is ready to
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// be exported. Returns the actual number of lines that were imported.
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int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
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const uint8_t* src, int src_stride);
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// Return true if there is pending output rows ready.
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static WEBP_INLINE
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int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
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return (rescaler->y_accum <= 0);
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}
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// Export one row from rescaler. Returns the pointer where output was written,
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// or NULL if no row was pending.
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uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk);
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// Export as many rows as possible. Return the numbers of rows written.
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int WebPRescalerExport(WebPRescaler* const wrk);
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif /* WEBP_UTILS_RESCALER_H_ */
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