gecko/gfx/2d/image_operations.cpp

391 lines
16 KiB
C++

// Copyright (c) 2006-2012 The Chromium Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google, Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this
// software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
#include "base/basictypes.h"
#include <algorithm>
#include <cmath>
#include <limits>
#include "image_operations.h"
#include "base/stack_container.h"
#include "convolver.h"
#include "skia/include/core/SkColorPriv.h"
#include "skia/include/core/SkBitmap.h"
#include "skia/include/core/SkRect.h"
#include "skia/include/core/SkFontHost.h"
namespace skia {
namespace resize {
// TODO(egouriou): Take advantage of periods in the convolution.
// Practical resizing filters are periodic outside of the border area.
// For Lanczos, a scaling by a (reduced) factor of p/q (q pixels in the
// source become p pixels in the destination) will have a period of p.
// A nice consequence is a period of 1 when downscaling by an integral
// factor. Downscaling from typical display resolutions is also bound
// to produce interesting periods as those are chosen to have multiple
// small factors.
// Small periods reduce computational load and improve cache usage if
// the coefficients can be shared. For periods of 1 we can consider
// loading the factors only once outside the borders.
void ComputeFilters(ImageOperations::ResizeMethod method,
int src_size, int dst_size,
int dest_subset_lo, int dest_subset_size,
ConvolutionFilter1D* output) {
// method_ will only ever refer to an "algorithm method".
SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
(method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
float scale = static_cast<float>(dst_size) / static_cast<float>(src_size);
int dest_subset_hi = dest_subset_lo + dest_subset_size; // [lo, hi)
// When we're doing a magnification, the scale will be larger than one. This
// means the destination pixels are much smaller than the source pixels, and
// that the range covered by the filter won't necessarily cover any source
// pixel boundaries. Therefore, we use these clamped values (max of 1) for
// some computations.
float clamped_scale = std::min(1.0f, scale);
float src_support = GetFilterSupport(method, clamped_scale) / clamped_scale;
// Speed up the divisions below by turning them into multiplies.
float inv_scale = 1.0f / scale;
StackVector<float, 64> filter_values;
StackVector<int16_t, 64> fixed_filter_values;
// Loop over all pixels in the output range. We will generate one set of
// filter values for each one. Those values will tell us how to blend the
// source pixels to compute the destination pixel.
for (int dest_subset_i = dest_subset_lo; dest_subset_i < dest_subset_hi;
dest_subset_i++) {
// Reset the arrays. We don't declare them inside so they can re-use the
// same malloc-ed buffer.
filter_values->clear();
fixed_filter_values->clear();
// This is the pixel in the source directly under the pixel in the dest.
// Note that we base computations on the "center" of the pixels. To see
// why, observe that the destination pixel at coordinates (0, 0) in a 5.0x
// downscale should "cover" the pixels around the pixel with *its center*
// at coordinates (2.5, 2.5) in the source, not those around (0, 0).
// Hence we need to scale coordinates (0.5, 0.5), not (0, 0).
float src_pixel = (static_cast<float>(dest_subset_i) + 0.5f) * inv_scale;
// Compute the (inclusive) range of source pixels the filter covers.
int src_begin = std::max(0, FloorInt(src_pixel - src_support));
int src_end = std::min(src_size - 1, CeilInt(src_pixel + src_support));
// Compute the unnormalized filter value at each location of the source
// it covers.
float filter_sum = 0.0f; // Sub of the filter values for normalizing.
for (int cur_filter_pixel = src_begin; cur_filter_pixel <= src_end;
cur_filter_pixel++) {
// Distance from the center of the filter, this is the filter coordinate
// in source space. We also need to consider the center of the pixel
// when comparing distance against 'src_pixel'. In the 5x downscale
// example used above the distance from the center of the filter to
// the pixel with coordinates (2, 2) should be 0, because its center
// is at (2.5, 2.5).
float src_filter_dist =
((static_cast<float>(cur_filter_pixel) + 0.5f) - src_pixel);
// Since the filter really exists in dest space, map it there.
float dest_filter_dist = src_filter_dist * clamped_scale;
// Compute the filter value at that location.
float filter_value = ComputeFilter(method, dest_filter_dist);
filter_values->push_back(filter_value);
filter_sum += filter_value;
}
// The filter must be normalized so that we don't affect the brightness of
// the image. Convert to normalized fixed point.
int16_t fixed_sum = 0;
for (size_t i = 0; i < filter_values->size(); i++) {
int16_t cur_fixed = output->FloatToFixed(filter_values[i] / filter_sum);
fixed_sum += cur_fixed;
fixed_filter_values->push_back(cur_fixed);
}
// The conversion to fixed point will leave some rounding errors, which
// we add back in to avoid affecting the brightness of the image. We
// arbitrarily add this to the center of the filter array (this won't always
// be the center of the filter function since it could get clipped on the
// edges, but it doesn't matter enough to worry about that case).
int16_t leftovers = output->FloatToFixed(1.0f) - fixed_sum;
fixed_filter_values[fixed_filter_values->size() / 2] += leftovers;
// Now it's ready to go.
output->AddFilter(src_begin, &fixed_filter_values[0],
static_cast<int>(fixed_filter_values->size()));
}
output->PaddingForSIMD(8);
}
} // namespace resize
ImageOperations::ResizeMethod ResizeMethodToAlgorithmMethod(
ImageOperations::ResizeMethod method) {
// Convert any "Quality Method" into an "Algorithm Method"
if (method >= ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD &&
method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD) {
return method;
}
// The call to ImageOperationsGtv::Resize() above took care of
// GPU-acceleration in the cases where it is possible. So now we just
// pick the appropriate software method for each resize quality.
switch (method) {
// Users of RESIZE_GOOD are willing to trade a lot of quality to
// get speed, allowing the use of linear resampling to get hardware
// acceleration (SRB). Hence any of our "good" software filters
// will be acceptable, and we use the fastest one, Hamming-1.
case ImageOperations::RESIZE_GOOD:
// Users of RESIZE_BETTER are willing to trade some quality in order
// to improve performance, but are guaranteed not to devolve to a linear
// resampling. In visual tests we see that Hamming-1 is not as good as
// Lanczos-2, however it is about 40% faster and Lanczos-2 itself is
// about 30% faster than Lanczos-3. The use of Hamming-1 has been deemed
// an acceptable trade-off between quality and speed.
case ImageOperations::RESIZE_BETTER:
return ImageOperations::RESIZE_HAMMING1;
default:
return ImageOperations::RESIZE_LANCZOS3;
}
}
// Resize ----------------------------------------------------------------------
// static
SkBitmap ImageOperations::Resize(const SkBitmap& source,
ResizeMethod method,
int dest_width, int dest_height,
const SkIRect& dest_subset,
void* dest_pixels /* = nullptr */) {
if (method == ImageOperations::RESIZE_SUBPIXEL)
return ResizeSubpixel(source, dest_width, dest_height, dest_subset);
else
return ResizeBasic(source, method, dest_width, dest_height, dest_subset,
dest_pixels);
}
// static
SkBitmap ImageOperations::ResizeSubpixel(const SkBitmap& source,
int dest_width, int dest_height,
const SkIRect& dest_subset) {
// Currently only works on Linux/BSD because these are the only platforms
// where SkFontHost::GetSubpixelOrder is defined.
#if defined(XP_UNIX)
// Understand the display.
const SkFontHost::LCDOrder order = SkFontHost::GetSubpixelOrder();
const SkFontHost::LCDOrientation orientation =
SkFontHost::GetSubpixelOrientation();
// Decide on which dimension, if any, to deploy subpixel rendering.
int w = 1;
int h = 1;
switch (orientation) {
case SkFontHost::kHorizontal_LCDOrientation:
w = dest_width < source.width() ? 3 : 1;
break;
case SkFontHost::kVertical_LCDOrientation:
h = dest_height < source.height() ? 3 : 1;
break;
}
// Resize the image.
const int width = dest_width * w;
const int height = dest_height * h;
SkIRect subset = { dest_subset.fLeft, dest_subset.fTop,
dest_subset.fLeft + dest_subset.width() * w,
dest_subset.fTop + dest_subset.height() * h };
SkBitmap img = ResizeBasic(source, ImageOperations::RESIZE_LANCZOS3, width,
height, subset);
const int row_words = img.rowBytes() / 4;
if (w == 1 && h == 1)
return img;
// Render into subpixels.
SkBitmap result;
SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
dest_subset.height(),
kBGRA_8888_SkColorType,
kPremul_SkAlphaType);
result.allocPixels(info);
if (!result.readyToDraw())
return img;
SkAutoLockPixels locker(img);
if (!img.readyToDraw())
return img;
uint32_t* src_row = img.getAddr32(0, 0);
uint32_t* dst_row = result.getAddr32(0, 0);
for (int y = 0; y < dest_subset.height(); y++) {
uint32_t* src = src_row;
uint32_t* dst = dst_row;
for (int x = 0; x < dest_subset.width(); x++, src += w, dst++) {
uint8_t r = 0, g = 0, b = 0, a = 0;
switch (order) {
case SkFontHost::kRGB_LCDOrder:
switch (orientation) {
case SkFontHost::kHorizontal_LCDOrientation:
r = SkGetPackedR32(src[0]);
g = SkGetPackedG32(src[1]);
b = SkGetPackedB32(src[2]);
a = SkGetPackedA32(src[1]);
break;
case SkFontHost::kVertical_LCDOrientation:
r = SkGetPackedR32(src[0 * row_words]);
g = SkGetPackedG32(src[1 * row_words]);
b = SkGetPackedB32(src[2 * row_words]);
a = SkGetPackedA32(src[1 * row_words]);
break;
}
break;
case SkFontHost::kBGR_LCDOrder:
switch (orientation) {
case SkFontHost::kHorizontal_LCDOrientation:
b = SkGetPackedB32(src[0]);
g = SkGetPackedG32(src[1]);
r = SkGetPackedR32(src[2]);
a = SkGetPackedA32(src[1]);
break;
case SkFontHost::kVertical_LCDOrientation:
b = SkGetPackedB32(src[0 * row_words]);
g = SkGetPackedG32(src[1 * row_words]);
r = SkGetPackedR32(src[2 * row_words]);
a = SkGetPackedA32(src[1 * row_words]);
break;
}
break;
case SkFontHost::kNONE_LCDOrder:
break;
}
// Premultiplied alpha is very fragile.
a = a > r ? a : r;
a = a > g ? a : g;
a = a > b ? a : b;
*dst = SkPackARGB32(a, r, g, b);
}
src_row += h * row_words;
dst_row += result.rowBytes() / 4;
}
result.setAlphaType(img.alphaType());
return result;
#else
return SkBitmap();
#endif // OS_POSIX && !OS_MACOSX && !defined(OS_ANDROID)
}
// static
SkBitmap ImageOperations::ResizeBasic(const SkBitmap& source,
ResizeMethod method,
int dest_width, int dest_height,
const SkIRect& dest_subset,
void* dest_pixels /* = nullptr */) {
// Ensure that the ResizeMethod enumeration is sound.
SkASSERT(((RESIZE_FIRST_QUALITY_METHOD <= method) &&
(method <= RESIZE_LAST_QUALITY_METHOD)) ||
((RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
(method <= RESIZE_LAST_ALGORITHM_METHOD)));
// If the size of source or destination is 0, i.e. 0x0, 0xN or Nx0, just
// return empty.
if (source.width() < 1 || source.height() < 1 ||
dest_width < 1 || dest_height < 1)
return SkBitmap();
method = ResizeMethodToAlgorithmMethod(method);
// Check that we deal with an "algorithm methods" from this point onward.
SkASSERT((ImageOperations::RESIZE_FIRST_ALGORITHM_METHOD <= method) &&
(method <= ImageOperations::RESIZE_LAST_ALGORITHM_METHOD));
SkAutoLockPixels locker(source);
if (!source.readyToDraw())
return SkBitmap();
ConvolutionFilter1D x_filter;
ConvolutionFilter1D y_filter;
resize::ComputeFilters(method, source.width(), dest_width, dest_subset.fLeft, dest_subset.width(), &x_filter);
resize::ComputeFilters(method, source.height(), dest_height, dest_subset.fTop, dest_subset.height(), &y_filter);
// Get a source bitmap encompassing this touched area. We construct the
// offsets and row strides such that it looks like a new bitmap, while
// referring to the old data.
const uint8_t* source_subset =
reinterpret_cast<const uint8_t*>(source.getPixels());
// Convolve into the result.
SkBitmap result;
SkImageInfo info = SkImageInfo::Make(dest_subset.width(),
dest_subset.height(),
kBGRA_8888_SkColorType,
kPremul_SkAlphaType);
if (dest_pixels) {
result.installPixels(info, dest_pixels, info.minRowBytes());
} else {
result.allocPixels(info);
}
if (!result.readyToDraw())
return SkBitmap();
BGRAConvolve2D(source_subset, static_cast<int>(source.rowBytes()),
!source.isOpaque(), x_filter, y_filter,
static_cast<int>(result.rowBytes()),
static_cast<unsigned char*>(result.getPixels()));
// Preserve the "opaque" flag for use as an optimization later.
result.setAlphaType(source.alphaType());
return result;
}
// static
SkBitmap ImageOperations::Resize(const SkBitmap& source,
ResizeMethod method,
int dest_width, int dest_height,
void* dest_pixels /* = nullptr */) {
SkIRect dest_subset = { 0, 0, dest_width, dest_height };
return Resize(source, method, dest_width, dest_height, dest_subset,
dest_pixels);
}
} // namespace skia