386 lines
16 KiB
C++
386 lines
16 KiB
C++
// Copyright (c) 2006-2012 The Chromium Authors. All rights reserved.
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// Copyright (c) 2018 Mark Straver BASc. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in
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// the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google, Inc. nor the names of its contributors
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// may be used to endorse or promote products derived from this
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// software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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#include "base/basictypes.h"
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#include <algorithm>
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#include <cmath>
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#include <limits>
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#include "image_operations.h"
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#include "base/stack_container.h"
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#include "convolver.h"
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#include "skia/include/core/SkColorPriv.h"
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#include "skia/include/core/SkBitmap.h"
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#include "skia/include/core/SkRect.h"
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#include "skia/include/core/SkFontLCDConfig.h"
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namespace skia {
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namespace resize {
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// TODO(egouriou): Take advantage of periods in the convolution.
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// Practical resizing filters are periodic outside of the border area.
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// For Lanczos, a scaling by a (reduced) factor of p/q (q pixels in the
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// source become p pixels in the destination) will have a period of p.
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// A nice consequence is a period of 1 when downscaling by an integral
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// factor. Downscaling from typical display resolutions is also bound
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// to produce interesting periods as those are chosen to have multiple
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// small factors.
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// Small periods reduce computational load and improve cache usage if
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// the coefficients can be shared. For periods of 1 we can consider
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// loading the factors only once outside the borders.
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void ComputeFilters(ImageOperations::ResizeMethod method,
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int src_size, int dst_size,
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int dest_subset_lo, int dest_subset_size,
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ConvolutionFilter1D* output) {
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// method_ will only ever refer to an "algorithm method".
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SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
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(method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
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float scale = static_cast<float>(dst_size) / static_cast<float>(src_size);
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int dest_subset_hi = dest_subset_lo + dest_subset_size; // [lo, hi)
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// When we're doing a magnification, the scale will be larger than one. This
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// means the destination pixels are much smaller than the source pixels, and
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// that the range covered by the filter won't necessarily cover any source
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// pixel boundaries. Therefore, we use these clamped values (max of 1) for
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// some computations.
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float clamped_scale = std::min(1.0f, scale);
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float src_support = GetFilterSupport(method, clamped_scale) / clamped_scale;
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// Speed up the divisions below by turning them into multiplies.
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float inv_scale = 1.0f / scale;
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StackVector<float, 64> filter_values;
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StackVector<int16_t, 64> fixed_filter_values;
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// Loop over all pixels in the output range. We will generate one set of
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// filter values for each one. Those values will tell us how to blend the
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// source pixels to compute the destination pixel.
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for (int dest_subset_i = dest_subset_lo; dest_subset_i < dest_subset_hi;
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dest_subset_i++) {
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// Reset the arrays. We don't declare them inside so they can re-use the
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// same malloc-ed buffer.
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filter_values->clear();
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fixed_filter_values->clear();
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// This is the pixel in the source directly under the pixel in the dest.
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// Note that we base computations on the "center" of the pixels. To see
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// why, observe that the destination pixel at coordinates (0, 0) in a 5.0x
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// downscale should "cover" the pixels around the pixel with *its center*
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// at coordinates (2.5, 2.5) in the source, not those around (0, 0).
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// Hence we need to scale coordinates (0.5, 0.5), not (0, 0).
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float src_pixel = (static_cast<float>(dest_subset_i) + 0.5f) * inv_scale;
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// Compute the (inclusive) range of source pixels the filter covers.
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int src_begin = std::max(0, FloorInt(src_pixel - src_support));
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int src_end = std::min(src_size - 1, CeilInt(src_pixel + src_support));
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// Compute the unnormalized filter value at each location of the source
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// it covers.
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float filter_sum = 0.0f; // Sum of the filter values for normalizing.
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for (int cur_filter_pixel = src_begin; cur_filter_pixel <= src_end;
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cur_filter_pixel++) {
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// Distance from the center of the filter, this is the filter coordinate
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// in source space. We also need to consider the center of the pixel
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// when comparing distance against 'src_pixel'. In the 5x downscale
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// example used above the distance from the center of the filter to
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// the pixel with coordinates (2, 2) should be 0, because its center
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// is at (2.5, 2.5).
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float src_filter_dist =
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((static_cast<float>(cur_filter_pixel) + 0.5f) - src_pixel);
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// Since the filter really exists in dest space, map it there.
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float dest_filter_dist = src_filter_dist * clamped_scale;
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// Compute the filter value at that location.
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float filter_value = ComputeFilter(method, dest_filter_dist);
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filter_values->push_back(filter_value);
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filter_sum += filter_value;
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}
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// The filter must be normalized so that we don't affect the brightness of
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// the image. Convert to normalized fixed point.
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int16_t fixed_sum = 0;
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for (size_t i = 0; i < filter_values->size(); i++) {
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int16_t cur_fixed = output->FloatToFixed(filter_values[i] / filter_sum);
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fixed_sum += cur_fixed;
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fixed_filter_values->push_back(cur_fixed);
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}
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// The conversion to fixed point will leave some rounding errors, which
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// we add back in to avoid affecting the brightness of the image. We
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// arbitrarily add this to the center of the filter array (this won't always
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// be the center of the filter function since it could get clipped on the
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// edges, but it doesn't matter enough to worry about that case).
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int16_t leftovers = output->FloatToFixed(1.0f) - fixed_sum;
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fixed_filter_values[fixed_filter_values->size() / 2] += leftovers;
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// Now it's ready to go.
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output->AddFilter(src_begin, &fixed_filter_values[0],
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static_cast<int>(fixed_filter_values->size()));
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}
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output->PaddingForSIMD(8);
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}
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} // namespace resize
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ImageOperations::ResizeMethod ResizeMethodToAlgorithmMethod(
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ImageOperations::ResizeMethod method) {
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// If we already have an "Algorithm Method", just return that.
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if (method >= ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD &&
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method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD) {
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return method;
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}
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// Convert any "Quality Method" into an "Algorithm Method"
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switch (method) {
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case ImageOperations::RESIZE_GOOD:
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// Users of RESIZE_GOOD are willing to trade quality to get speed.
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// In visual tests we see that Hamming-1 is not as good as
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// Lanczos-2, however it is about 40% faster, and Lanczos-2 itself is
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// about 30% faster than Lanczos-3. The use of Hamming-1 has been deemed
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// an unacceptable trade-off between quality and speed due to the limited
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// pixel space it operates in, so we pick Lanczos-2 here.
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case ImageOperations::RESIZE_BETTER:
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return ImageOperations::RESIZE_LANCZOS2;
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default:
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return ImageOperations::RESIZE_LANCZOS3;
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}
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}
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// Resize ----------------------------------------------------------------------
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// static
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SkBitmap ImageOperations::Resize(const SkBitmap& source,
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ResizeMethod method,
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int dest_width, int dest_height,
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const SkIRect& dest_subset,
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void* dest_pixels /* = nullptr */) {
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if (method == ImageOperations::RESIZE_SUBPIXEL)
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return ResizeSubpixel(source, dest_width, dest_height, dest_subset);
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else
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return ResizeBasic(source, method, dest_width, dest_height, dest_subset,
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dest_pixels);
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}
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// static
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SkBitmap ImageOperations::ResizeSubpixel(const SkBitmap& source,
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int dest_width, int dest_height,
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const SkIRect& dest_subset) {
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// Currently only works on Linux/BSD because these are the only platforms
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// where SkFontLCDConfig::GetSubpixelOrder is defined.
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#if defined(XP_UNIX)
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// Understand the display.
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const SkFontLCDConfig::LCDOrder order = SkFontLCDConfig::GetSubpixelOrder();
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const SkFontLCDConfig::LCDOrientation orientation =
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SkFontLCDConfig::GetSubpixelOrientation();
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// Decide on which dimension, if any, to deploy subpixel rendering.
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int w = 1;
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int h = 1;
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switch (orientation) {
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case SkFontLCDConfig::kHorizontal_LCDOrientation:
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w = dest_width < source.width() ? 3 : 1;
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break;
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case SkFontLCDConfig::kVertical_LCDOrientation:
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h = dest_height < source.height() ? 3 : 1;
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break;
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}
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// Resize the image.
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const int width = dest_width * w;
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const int height = dest_height * h;
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SkIRect subset = { dest_subset.fLeft, dest_subset.fTop,
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dest_subset.fLeft + dest_subset.width() * w,
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dest_subset.fTop + dest_subset.height() * h };
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SkBitmap img = ResizeBasic(source, ImageOperations::RESIZE_LANCZOS3, width,
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height, subset);
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const int row_words = img.rowBytes() / 4;
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if (w == 1 && h == 1)
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return img;
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// Render into subpixels.
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SkBitmap result;
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SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
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dest_subset.height(),
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kBGRA_8888_SkColorType,
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kPremul_SkAlphaType);
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result.allocPixels(info);
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if (!result.readyToDraw())
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return img;
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SkAutoLockPixels locker(img);
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if (!img.readyToDraw())
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return img;
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uint32_t* src_row = img.getAddr32(0, 0);
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uint32_t* dst_row = result.getAddr32(0, 0);
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for (int y = 0; y < dest_subset.height(); y++) {
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uint32_t* src = src_row;
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uint32_t* dst = dst_row;
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for (int x = 0; x < dest_subset.width(); x++, src += w, dst++) {
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uint8_t r = 0, g = 0, b = 0, a = 0;
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switch (order) {
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case SkFontLCDConfig::kRGB_LCDOrder:
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switch (orientation) {
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case SkFontLCDConfig::kHorizontal_LCDOrientation:
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r = SkGetPackedR32(src[0]);
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g = SkGetPackedG32(src[1]);
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b = SkGetPackedB32(src[2]);
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a = SkGetPackedA32(src[1]);
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break;
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case SkFontLCDConfig::kVertical_LCDOrientation:
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r = SkGetPackedR32(src[0 * row_words]);
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g = SkGetPackedG32(src[1 * row_words]);
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b = SkGetPackedB32(src[2 * row_words]);
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a = SkGetPackedA32(src[1 * row_words]);
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break;
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}
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break;
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case SkFontLCDConfig::kBGR_LCDOrder:
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switch (orientation) {
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case SkFontLCDConfig::kHorizontal_LCDOrientation:
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b = SkGetPackedB32(src[0]);
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g = SkGetPackedG32(src[1]);
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r = SkGetPackedR32(src[2]);
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a = SkGetPackedA32(src[1]);
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break;
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case SkFontLCDConfig::kVertical_LCDOrientation:
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b = SkGetPackedB32(src[0 * row_words]);
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g = SkGetPackedG32(src[1 * row_words]);
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r = SkGetPackedR32(src[2 * row_words]);
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a = SkGetPackedA32(src[1 * row_words]);
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break;
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}
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break;
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case SkFontLCDConfig::kNONE_LCDOrder:
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break;
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}
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// Premultiplied alpha is very fragile.
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a = a > r ? a : r;
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a = a > g ? a : g;
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a = a > b ? a : b;
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*dst = SkPackARGB32(a, r, g, b);
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}
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src_row += h * row_words;
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dst_row += result.rowBytes() / 4;
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}
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result.setAlphaType(img.alphaType());
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return result;
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#else
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return SkBitmap();
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#endif // OS_POSIX && !OS_MACOSX && !defined(OS_ANDROID)
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}
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// static
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SkBitmap ImageOperations::ResizeBasic(const SkBitmap& source,
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ResizeMethod method,
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int dest_width, int dest_height,
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const SkIRect& dest_subset,
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void* dest_pixels /* = nullptr */) {
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// Ensure that the ResizeMethod enumeration is sound.
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SkASSERT(((RESIZE_FIRST_QUALITY_METHOD <= method) &&
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(method <= RESIZE_LAST_QUALITY_METHOD)) ||
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((RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
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(method <= RESIZE_LAST_ALGORITHM_METHOD)));
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// If the size of source or destination is 0, i.e. 0x0, 0xN or Nx0, just
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// return empty.
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if (source.width() < 1 || source.height() < 1 ||
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dest_width < 1 || dest_height < 1)
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return SkBitmap();
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method = ResizeMethodToAlgorithmMethod(method);
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// Check that we deal with an "algorithm methods" from this point onward.
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SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
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(method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
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SkAutoLockPixels locker(source);
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if (!source.readyToDraw())
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return SkBitmap();
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ConvolutionFilter1D x_filter;
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ConvolutionFilter1D y_filter;
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resize::ComputeFilters(method, source.width(), dest_width, dest_subset.fLeft, dest_subset.width(), &x_filter);
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resize::ComputeFilters(method, source.height(), dest_height, dest_subset.fTop, dest_subset.height(), &y_filter);
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// Get a source bitmap encompassing this touched area. We construct the
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// offsets and row strides such that it looks like a new bitmap, while
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// referring to the old data.
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const uint8_t* source_subset =
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reinterpret_cast<const uint8_t*>(source.getPixels());
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// Convolve into the result.
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SkBitmap result;
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SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
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dest_subset.height(),
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kBGRA_8888_SkColorType,
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kPremul_SkAlphaType);
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if (dest_pixels) {
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result.installPixels(info, dest_pixels, info.minRowBytes());
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} else {
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result.allocPixels(info);
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}
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if (!result.readyToDraw())
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return SkBitmap();
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BGRAConvolve2D(source_subset, static_cast<int>(source.rowBytes()),
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!source.isOpaque(), x_filter, y_filter,
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static_cast<int>(result.rowBytes()),
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static_cast<unsigned char*>(result.getPixels()));
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// Preserve the "opaque" flag for use as an optimization later.
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result.setAlphaType(source.alphaType());
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return result;
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}
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// static
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SkBitmap ImageOperations::Resize(const SkBitmap& source,
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ResizeMethod method,
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int dest_width, int dest_height,
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void* dest_pixels /* = nullptr */) {
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SkIRect dest_subset = { 0, 0, dest_width, dest_height };
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return Resize(source, method, dest_width, dest_height, dest_subset,
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dest_pixels);
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}
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} // namespace skia
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