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78 lines
3.0 KiB
78 lines
3.0 KiB
// 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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