nerdcruft/libcruft-util
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libcruft-util/image.cpp

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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2011-2015 Danny Robson <danny@nerdcruft.net>
*/
#include "image.hpp"
#include "debug.hpp"
#include "except.hpp"
#include "io.hpp"
#include <fstream>
using util::image::buffer;
//-----------------------------------------------------------------------------
struct box {
static constexpr float support = 0.5f;
static constexpr float weight [[gnu::pure]] (float x)
{
return (x >= -0.5f && x <= 0.5f) ? 1.f : 0.f;
}
};
//-----------------------------------------------------------------------------
// XXX: Known to cause hard black ringing
template <size_t S>
struct lanczos {
static constexpr float support = float {S};
static float weight [[gnu::pure]] (float x)
{
if (x < 0.f)
x = -x;
if (x <= S)
return sincn (x) * sincn (x / S);
return 0.f;
}
};
template struct lanczos< 3>;
template struct lanczos< 4>;
template struct lanczos< 6>;
template struct lanczos<12>;
//-----------------------------------------------------------------------------
struct bspline {
static constexpr float support = 2.f;
static float weight [[gnu::pure]] (float x)
{
if (x < 0.f)
x = -x;
if (x < 1.f)
return .5f * x * x * x - x * x + (2.f / 3.f);
if (x < 2.f) {
x = 2.f - x;
return (1.f / 6.f) * x * x * x;
}
return 0.f;
}
};
//-----------------------------------------------------------------------------
// XXX: Known to cause hard black ringing
struct mitchell {
static constexpr float support = 2.f;
static float weight [[gnu::pure]] (float x)
{
return eval (x, 1.f / 3.f, 1.f / 3.f);
}
private:
static float eval (float x, float B, float C)
{
if (x < 0.f)
x = -x;
if (x < 1.f) {
x = ( 12.f - 9.f * B - 6.f * C) * x * x * x
+ (-18.f + 12.f * B + 6.f * C) * x * x
+ 6.f - 2.f * B;
return x / 6.f;
}
if (x < 2.f) {
x = ( -1.f * B - 6.f * C) * x * x * x
+ ( 6.f * B + 30.f * C) * x * x
+ (-12.f * B - 48.f * C) * x
+ 8.f * B + 24.f * C;
return x / 6.f;
}
return 0.f;
}
};
//-----------------------------------------------------------------------------
template <typename T>
util::image::buffer<T>::buffer (size_t _w, size_t _h, size_t _s):
w (_w),
h (_h),
s (_s),
m_data (std::make_unique<T[]> (_w * _s))
{
CHECK_NEQ (w * h, 0);
CHECK_GE (s, w);
}
//-----------------------------------------------------------------------------
template <typename T>
util::image::buffer<T>::buffer (size_t _w, size_t _h):
buffer<T> (_w, _h, _w)
{ ; }
//-----------------------------------------------------------------------------
template <typename T>
util::image::buffer<T>::buffer (size_t _w,
size_t _h,
size_t _s,
std::unique_ptr<T[]> &&_data):
w (_w),
h (_h),
s (_s),
m_data (std::move (_data))
{
CHECK_NEQ (w * h, 0);
CHECK_GE (s, w);
}
//-----------------------------------------------------------------------------
template <typename T>
template <typename U>
util::image::buffer<U>
util::image::buffer<T>::alloc (void) const
{
return buffer<U> (w, h, s);
}
//-----------------------------------------------------------------------------
template <typename T>
void
util::image::buffer<T>::fill (const T v)
{
std::fill (begin (), end (), v);
}
//-----------------------------------------------------------------------------
template <typename T, typename U>
static U
rescale (T v)
{
return v * sizeof (U) / sizeof (T);
}
//-----------------------------------------------------------------------------
template <typename T>
template <typename U>
util::image::buffer<U>
util::image::buffer<T>::clone (void) const
{
auto out = alloc<U> ();
std::transform (begin (), end (), out.begin (), renormalise<T,U>);
return out;
}
//-----------------------------------------------------------------------------
// HACK: This code hasn't really been tested with multiple filters (it is
// known to produce dark ringing artefacts with sinc) or robustly with
// fractional factors. But... it works more or less.
template <typename T>
util::image::buffer<T>
util::image::buffer<T>::downsample (float factor) const
{
CHECK_GE (factor, 0);
using filter = bspline;
const buffer &src = *this;
buffer dst (static_cast<size_t> (w / factor),
static_cast<size_t> (h / factor));
const float scale = float (dst.w) / src.w;
const float half_width = filter::support / scale;
const int half_pixels = int (std::ceil (half_width));
// Calculate the weighted sum of the src pixels for each dst pixel
for (size_t d_y = 0; d_y < dst.h; ++d_y)
for (size_t d_x = 0; d_x < dst.w; ++d_x) {
// Initialise value and weight sums
float v = 0.f;
float m = 0.f;
// Find the centre of the src pixel
float o_y = (d_y + 0.5f) / scale;
float o_x = (d_x + 0.5f) / scale;
// Do a full summation across the window. This isn't using
// seperable filtering because:
// a) we need high precision with fractional factors
// b) it's much easier to implement as is
//
// TODO: seperable filters
for (int s_y = -half_pixels; s_y <= half_pixels; ++s_y)
for (int s_x = -half_pixels; s_x <= half_pixels; ++s_x) {
float m_x = filter::weight (s_x * scale);
float m_y = filter::weight (s_y * scale);
float m_ = m_x * m_y;
// Simple clamp to border for edges
int x = int (limit (o_x + s_x - 0.5f, 0, src.w));
int y = int (limit (o_y + s_y - 0.5f, 0, src.h));
// Collection the contribution
v += m_ * src.m_data[y * src.s + x];
m += m_;
}
CHECK_NEZ (m);
dst.m_data[d_y * dst.s + d_x] = uint8_t (v / m);
}
return dst;
}
//-----------------------------------------------------------------------------
template <typename T>
T*
buffer<T>::data (void)
{
return begin ();
}
//-----------------------------------------------------------------------------
template <typename T>
T*
buffer<T>::begin (void)
{
return m_data.get ();
}
//-----------------------------------------------------------------------------
template <typename T>
T*
buffer<T>::end (void)
{
return begin () + h * s;
}
//-----------------------------------------------------------------------------
template <typename T>
const T*
buffer<T>::data (void) const
{
return begin ();
}
//-----------------------------------------------------------------------------
template <typename T>
const T*
buffer<T>::begin (void) const
{
return m_data.get ();
}
//-----------------------------------------------------------------------------
template <typename T>
const T*
buffer<T>::end (void) const
{
return begin () + h * s;
}
///////////////////////////////////////////////////////////////////////////////
// HACK: This does not support the full header structure with any robustness.
// In particular it will abort when it sees a comment. If you want better
// support use waif, or port its implementation.
util::image::buffer<uint8_t>
util::pgm::read (const boost::filesystem::path &path)
{
util::mapped_file raw (path);
std::ifstream cooked (path.string (), std::ios::binary);
char magic[2];
size_t width, height, scale;
char space;
cooked >> magic[0] >> magic[1] >> width >> height >> scale >> space;
if (magic[0] != 'P' && magic[1] != '5')
throw std::runtime_error ("invalid header magic");
if (width == 0 || height == 0 || scale == 0)
throw std::runtime_error ("zero width, height, or scale");
size_t expected = width * height;
size_t remain = raw.size () - cooked.tellg ();
if (expected != remain)
throw std::runtime_error ("expected data size mismatch");
util::image::buffer<uint8_t> out (width, height);
CHECK_EQ (out.w, out.s);
std::copy (raw.begin () + cooked.tellg () - 1, raw.end (), out.begin ());
return out;
}
//-----------------------------------------------------------------------------
static void
write_netpbm (const uint8_t *restrict pixels,
size_t width,
size_t height,
size_t stride,
const boost::filesystem::path &path,
const char* MAGIC) {
CHECK (pixels);
CHECK_GT (width, 0);
CHECK_GE (stride, width);
CHECK_GT (height, 0);
// Establish an output stream
std::ofstream output (path.string ());
if (!output.good ())
throw util::output_error ("Unable to open output file");
// Write the PPM header.
output << MAGIC << "\n"
<< width << "\n"
<< height << "\n"
<< (size_t)std::numeric_limits<uint8_t>::max () << "\n";
// Write the data rows
for (size_t y = 0; y < height; ++y) {
for (size_t x = 0; x < width; ++x)
output << pixels[y * stride + x];
}
}
//-----------------------------------------------------------------------------
void
util::pgm::write (const util::image::buffer<uint8_t> &src,
const boost::filesystem::path &path)
{
write (src.begin (), src.w, src.h, src.s, path);
}
//-----------------------------------------------------------------------------
void
util::pgm::write (const uint8_t *restrict pixels,
size_t width,
size_t height,
size_t stride,
const boost::filesystem::path &path) {
// TODO: We should switch between P2 (ascii) and P5 (binary)
static const char MAGIC[] = "P5";
write_netpbm (pixels, width, height, stride, path, MAGIC);
}
//-----------------------------------------------------------------------------
void
util::ppm::write (const uint8_t *restrict pixels,
size_t width,
size_t height,
size_t stride,
const boost::filesystem::path &path) {
// TODO: We should switch between P3 (ascii) and P6 (binary)
static const char MAGIC[] = "P6";
write_netpbm (pixels, width, height, stride, path, MAGIC);
}
//-----------------------------------------------------------------------------
template struct util::image::buffer<uint8_t>;
template struct util::image::buffer<float>;
template util::image::buffer<uint8_t> util::image::buffer<uint8_t>::alloc (void) const;
template util::image::buffer<uint8_t> util::image::buffer<uint8_t>::clone (void) const;
template util::image::buffer<uint8_t> util::image::buffer<float>::clone (void) const;
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