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Diffstat (limited to 'media/libwebp/utils/rescaler_utils.c')
| -rw-r--r-- | media/libwebp/utils/rescaler_utils.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/media/libwebp/utils/rescaler_utils.c b/media/libwebp/utils/rescaler_utils.c new file mode 100644 index 000000000..0d1f80da2 --- /dev/null +++ b/media/libwebp/utils/rescaler_utils.c @@ -0,0 +1,146 @@ +// Copyright 2012 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Rescaling functions +// +// Author: Skal (pascal.massimino@gmail.com) + +#include <assert.h> +#include <stdlib.h> +#include <string.h> +#include "../dsp/dsp.h" +#include "./rescaler_utils.h" + +//------------------------------------------------------------------------------ + +void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height, + uint8_t* const dst, + int dst_width, int dst_height, int dst_stride, + int num_channels, rescaler_t* const work) { + const int x_add = src_width, x_sub = dst_width; + const int y_add = src_height, y_sub = dst_height; + wrk->x_expand = (src_width < dst_width); + wrk->y_expand = (src_height < dst_height); + wrk->src_width = src_width; + wrk->src_height = src_height; + wrk->dst_width = dst_width; + wrk->dst_height = dst_height; + wrk->src_y = 0; + wrk->dst_y = 0; + wrk->dst = dst; + wrk->dst_stride = dst_stride; + wrk->num_channels = num_channels; + + // for 'x_expand', we use bilinear interpolation + wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add; + wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub; + if (!wrk->x_expand) { // fx_scale is not used otherwise + wrk->fx_scale = WEBP_RESCALER_FRAC(1, wrk->x_sub); + } + // vertical scaling parameters + wrk->y_add = wrk->y_expand ? y_add - 1 : y_add; + wrk->y_sub = wrk->y_expand ? y_sub - 1 : y_sub; + wrk->y_accum = wrk->y_expand ? wrk->y_sub : wrk->y_add; + if (!wrk->y_expand) { + // This is WEBP_RESCALER_FRAC(dst_height, x_add * y_add) without the cast. + // Its value is <= WEBP_RESCALER_ONE, because dst_height <= wrk->y_add, and + // wrk->x_add >= 1; + const uint64_t ratio = + (uint64_t)dst_height * WEBP_RESCALER_ONE / (wrk->x_add * wrk->y_add); + if (ratio != (uint32_t)ratio) { + // When ratio == WEBP_RESCALER_ONE, we can't represent the ratio with the + // current fixed-point precision. This happens when src_height == + // wrk->y_add (which == src_height), and wrk->x_add == 1. + // => We special-case fxy_scale = 0, in WebPRescalerExportRow(). + wrk->fxy_scale = 0; + } else { + wrk->fxy_scale = (uint32_t)ratio; + } + wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub); + } else { + wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add); + // wrk->fxy_scale is unused here. + } + wrk->irow = work; + wrk->frow = work + num_channels * dst_width; + memset(work, 0, 2 * dst_width * num_channels * sizeof(*work)); + + WebPRescalerDspInit(); +} + +int WebPRescalerGetScaledDimensions(int src_width, int src_height, + int* const scaled_width, + int* const scaled_height) { + assert(scaled_width != NULL); + assert(scaled_height != NULL); + { + int width = *scaled_width; + int height = *scaled_height; + + // if width is unspecified, scale original proportionally to height ratio. + if (width == 0) { + width = (src_width * height + src_height / 2) / src_height; + } + // if height is unspecified, scale original proportionally to width ratio. + if (height == 0) { + height = (src_height * width + src_width / 2) / src_width; + } + // Check if the overall dimensions still make sense. + if (width <= 0 || height <= 0) { + return 0; + } + + *scaled_width = width; + *scaled_height = height; + return 1; + } +} + +//------------------------------------------------------------------------------ +// all-in-one calls + +int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) { + const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub; + return (num_lines > max_num_lines) ? max_num_lines : num_lines; +} + +int WebPRescalerImport(WebPRescaler* const wrk, int num_lines, + const uint8_t* src, int src_stride) { + int total_imported = 0; + while (total_imported < num_lines && !WebPRescalerHasPendingOutput(wrk)) { + if (wrk->y_expand) { + rescaler_t* const tmp = wrk->irow; + wrk->irow = wrk->frow; + wrk->frow = tmp; + } + WebPRescalerImportRow(wrk, src); + if (!wrk->y_expand) { // Accumulate the contribution of the new row. + int x; + for (x = 0; x < wrk->num_channels * wrk->dst_width; ++x) { + wrk->irow[x] += wrk->frow[x]; + } + } + ++wrk->src_y; + src += src_stride; + ++total_imported; + wrk->y_accum -= wrk->y_sub; + } + return total_imported; +} + +int WebPRescalerExport(WebPRescaler* const rescaler) { + int total_exported = 0; + while (WebPRescalerHasPendingOutput(rescaler)) { + WebPRescalerExportRow(rescaler); + ++total_exported; + } + return total_exported; +} + +//------------------------------------------------------------------------------ |