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stb_image_resize.h
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/* stb_image_resize - v0.96 - public domain image resizing
by Jorge L Rodriguez (@VinoBS) - 2014
http://github.com/nothings/stb
Written with emphasis on usability, portability, and efficiency. (No
SIMD or threads, so it be easily outperformed by libs that use those.)
Only scaling and translation is supported, no rotations or shears.
Easy API downsamples w/Mitchell filter, upsamples w/cubic interpolation.
COMPILING & LINKING
In one C/C++ file that #includes this file, do this:
#define STB_IMAGE_RESIZE_IMPLEMENTATION
before the #include. That will create the implementation in that file.
QUICKSTART
stbir_resize_uint8( input_pixels , in_w , in_h , 0,
output_pixels, out_w, out_h, 0, num_channels)
stbir_resize_float(...)
stbir_resize_uint8_srgb( input_pixels , in_w , in_h , 0,
output_pixels, out_w, out_h, 0,
num_channels , alpha_chan , 0)
stbir_resize_uint8_srgb_edgemode(
input_pixels , in_w , in_h , 0,
output_pixels, out_w, out_h, 0,
num_channels , alpha_chan , 0, STBIR_EDGE_CLAMP)
// WRAP/REFLECT/ZERO
FULL API
See the "header file" section of the source for API documentation.
ADDITIONAL DOCUMENTATION
SRGB & FLOATING POINT REPRESENTATION
The sRGB functions presume IEEE floating point. If you do not have
IEEE floating point, define STBIR_NON_IEEE_FLOAT. This will use
a slower implementation.
MEMORY ALLOCATION
The resize functions here perform a single memory allocation using
malloc. To control the memory allocation, before the #include that
triggers the implementation, do:
#define STBIR_MALLOC(size,context) ...
#define STBIR_FREE(ptr,context) ...
Each resize function makes exactly one call to malloc/free, so to use
temp memory, store the temp memory in the context and return that.
ASSERT
Define STBIR_ASSERT(boolval) to override assert() and not use assert.h
OPTIMIZATION
Define STBIR_SATURATE_INT to compute clamp values in-range using
integer operations instead of float operations. This may be faster
on some platforms.
DEFAULT FILTERS
For functions which don't provide explicit control over what filters
to use, you can change the compile-time defaults with
#define STBIR_DEFAULT_FILTER_UPSAMPLE STBIR_FILTER_something
#define STBIR_DEFAULT_FILTER_DOWNSAMPLE STBIR_FILTER_something
See stbir_filter in the header-file section for the list of filters.
NEW FILTERS
A number of 1D filter kernels are used. For a list of
supported filters see the stbir_filter enum. To add a new filter,
write a filter function and add it to stbir__filter_info_table.
PROGRESS
For interactive use with slow resize operations, you can install
a progress-report callback:
#define STBIR_PROGRESS_REPORT(val) some_func(val)
The parameter val is a float which goes from 0 to 1 as progress is made.
For example:
static void my_progress_report(float progress);
#define STBIR_PROGRESS_REPORT(val) my_progress_report(val)
#define STB_IMAGE_RESIZE_IMPLEMENTATION
#include "stb_image_resize.h"
static void my_progress_report(float progress)
{
printf("Progress: %f%%\n", progress*100);
}
MAX CHANNELS
If your image has more than 64 channels, define STBIR_MAX_CHANNELS
to the max you'll have.
ALPHA CHANNEL
Most of the resizing functions provide the ability to control how
the alpha channel of an image is processed. The important things
to know about this:
1. The best mathematically-behaved version of alpha to use is
called "premultiplied alpha", in which the other color channels
have had the alpha value multiplied in. If you use premultiplied
alpha, linear filtering (such as image resampling done by this
library, or performed in texture units on GPUs) does the "right
thing". While premultiplied alpha is standard in the movie CGI
industry, it is still uncommon in the videogame/real-time world.
If you linearly filter non-premultiplied alpha, strange effects
occur. (For example, the 50/50 average of 99% transparent bright green
and 1% transparent black produces 50% transparent dark green when
non-premultiplied, whereas premultiplied it produces 50%
transparent near-black. The former introduces green energy
that doesn't exist in the source image.)
2. Artists should not edit premultiplied-alpha images; artists
want non-premultiplied alpha images. Thus, art tools generally output
non-premultiplied alpha images.
3. You will get best results in most cases by converting images
to premultiplied alpha before processing them mathematically.
4. If you pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED, the
resizer does not do anything special for the alpha channel;
it is resampled identically to other channels. This produces
the correct results for premultiplied-alpha images, but produces
less-than-ideal results for non-premultiplied-alpha images.
5. If you do not pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED,
then the resizer weights the contribution of input pixels
based on their alpha values, or, equivalently, it multiplies
the alpha value into the color channels, resamples, then divides
by the resultant alpha value. Input pixels which have alpha=0 do
not contribute at all to output pixels unless _all_ of the input
pixels affecting that output pixel have alpha=0, in which case
the result for that pixel is the same as it would be without
STBIR_FLAG_ALPHA_PREMULTIPLIED. However, this is only true for
input images in integer formats. For input images in float format,
input pixels with alpha=0 have no effect, and output pixels
which have alpha=0 will be 0 in all channels. (For float images,
you can manually achieve the same result by adding a tiny epsilon
value to the alpha channel of every image, and then subtracting
or clamping it at the end.)
6. You can suppress the behavior described in #5 and make
all-0-alpha pixels have 0 in all channels by #defining
STBIR_NO_ALPHA_EPSILON.
7. You can separately control whether the alpha channel is
interpreted as linear or affected by the colorspace. By default
it is linear; you almost never want to apply the colorspace.
(For example, graphics hardware does not apply sRGB conversion
to the alpha channel.)
CONTRIBUTORS
Jorge L Rodriguez: Implementation
Sean Barrett: API design, optimizations
Aras Pranckevicius: bugfix
Nathan Reed: warning fixes
REVISIONS
0.97 (2020-02-02) fixed warning
0.96 (2019-03-04) fixed warnings
0.95 (2017-07-23) fixed warnings
0.94 (2017-03-18) fixed warnings
0.93 (2017-03-03) fixed bug with certain combinations of heights
0.92 (2017-01-02) fix integer overflow on large (>2GB) images
0.91 (2016-04-02) fix warnings; fix handling of subpixel regions
0.90 (2014-09-17) first released version
LICENSE
See end of file for license information.
TODO
Don't decode all of the image data when only processing a partial tile
Don't use full-width decode buffers when only processing a partial tile
When processing wide images, break processing into tiles so data fits in L1 cache
Installable filters?
Resize that respects alpha test coverage
(Reference code: FloatImage::alphaTestCoverage and FloatImage::scaleAlphaToCoverage:
https://code.google.com/p/nvidia-texture-tools/source/browse/trunk/src/nvimage/FloatImage.cpp )
*/
#ifndef STBIR_INCLUDE_STB_IMAGE_RESIZE_H
#define STBIR_INCLUDE_STB_IMAGE_RESIZE_H
#ifdef _MSC_VER
typedef unsigned char stbir_uint8;
typedef unsigned short stbir_uint16;
typedef unsigned int stbir_uint32;
#else
#include <stdint.h>
typedef uint8_t stbir_uint8;
typedef uint16_t stbir_uint16;
typedef uint32_t stbir_uint32;
#endif
#ifndef STBIRDEF
#ifdef STB_IMAGE_RESIZE_STATIC
#define STBIRDEF static
#else
#ifdef __cplusplus
#define STBIRDEF extern "C"
#else
#define STBIRDEF extern
#endif
#endif
#endif
//////////////////////////////////////////////////////////////////////////////
//
// Easy-to-use API:
//
// * "input pixels" points to an array of image data with 'num_channels' channels (e.g. RGB=3, RGBA=4)
// * input_w is input image width (x-axis), input_h is input image height (y-axis)
// * stride is the offset between successive rows of image data in memory, in bytes. you can
// specify 0 to mean packed continuously in memory
// * alpha channel is treated identically to other channels.
// * colorspace is linear or sRGB as specified by function name
// * returned result is 1 for success or 0 in case of an error.
// #define STBIR_ASSERT() to trigger an assert on parameter validation errors.
// * Memory required grows approximately linearly with input and output size, but with
// discontinuities at input_w == output_w and input_h == output_h.
// * These functions use a "default" resampling filter defined at compile time. To change the filter,
// you can change the compile-time defaults by #defining STBIR_DEFAULT_FILTER_UPSAMPLE
// and STBIR_DEFAULT_FILTER_DOWNSAMPLE, or you can use the medium-complexity API.
STBIRDEF int stbir_resize_uint8( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
int num_channels);
STBIRDEF int stbir_resize_float( const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
float *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
int num_channels);
// The following functions interpret image data as gamma-corrected sRGB.
// Specify STBIR_ALPHA_CHANNEL_NONE if you have no alpha channel,
// or otherwise provide the index of the alpha channel. Flags value
// of 0 will probably do the right thing if you're not sure what
// the flags mean.
#define STBIR_ALPHA_CHANNEL_NONE -1
// Set this flag if your texture has premultiplied alpha. Otherwise, stbir will
// use alpha-weighted resampling (effectively premultiplying, resampling,
// then unpremultiplying).
#define STBIR_FLAG_ALPHA_PREMULTIPLIED (1 << 0)
// The specified alpha channel should be handled as gamma-corrected value even
// when doing sRGB operations.
#define STBIR_FLAG_ALPHA_USES_COLORSPACE (1 << 1)
STBIRDEF int stbir_resize_uint8_srgb(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
int num_channels, int alpha_channel, int flags);
typedef enum
{
STBIR_EDGE_CLAMP = 1,
STBIR_EDGE_REFLECT = 2,
STBIR_EDGE_WRAP = 3,
STBIR_EDGE_ZERO = 4,
} stbir_edge;
// This function adds the ability to specify how requests to sample off the edge of the image are handled.
STBIRDEF int stbir_resize_uint8_srgb_edgemode(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_wrap_mode);
//////////////////////////////////////////////////////////////////////////////
//
// Medium-complexity API
//
// This extends the easy-to-use API as follows:
//
// * Alpha-channel can be processed separately
// * If alpha_channel is not STBIR_ALPHA_CHANNEL_NONE
// * Alpha channel will not be gamma corrected (unless flags&STBIR_FLAG_GAMMA_CORRECT)
// * Filters will be weighted by alpha channel (unless flags&STBIR_FLAG_ALPHA_PREMULTIPLIED)
// * Filter can be selected explicitly
// * uint16 image type
// * sRGB colorspace available for all types
// * context parameter for passing to STBIR_MALLOC
typedef enum
{
STBIR_FILTER_DEFAULT = 0, // use same filter type that easy-to-use API chooses
STBIR_FILTER_BOX = 1, // A trapezoid w/1-pixel wide ramps, same result as box for integer scale ratios
STBIR_FILTER_TRIANGLE = 2, // On upsampling, produces same results as bilinear texture filtering
STBIR_FILTER_CUBICBSPLINE = 3, // The cubic b-spline (aka Mitchell-Netrevalli with B=1,C=0), gaussian-esque
STBIR_FILTER_CATMULLROM = 4, // An interpolating cubic spline
STBIR_FILTER_MITCHELL = 5, // Mitchell-Netrevalli filter with B=1/3, C=1/3
} stbir_filter;
typedef enum
{
STBIR_COLORSPACE_LINEAR,
STBIR_COLORSPACE_SRGB,
STBIR_MAX_COLORSPACES,
} stbir_colorspace;
// The following functions are all identical except for the type of the image data
STBIRDEF int stbir_resize_uint8_generic( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
void *alloc_context);
STBIRDEF int stbir_resize_uint16_generic(const stbir_uint16 *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
stbir_uint16 *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
void *alloc_context);
STBIRDEF int stbir_resize_float_generic( const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
float *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
void *alloc_context);
//////////////////////////////////////////////////////////////////////////////
//
// Full-complexity API
//
// This extends the medium API as follows:
//
// * uint32 image type
// * not typesafe
// * separate filter types for each axis
// * separate edge modes for each axis
// * can specify scale explicitly for subpixel correctness
// * can specify image source tile using texture coordinates
typedef enum
{
STBIR_TYPE_UINT8 ,
STBIR_TYPE_UINT16,
STBIR_TYPE_UINT32,
STBIR_TYPE_FLOAT ,
STBIR_MAX_TYPES
} stbir_datatype;
STBIRDEF int stbir_resize( const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
stbir_datatype datatype,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
stbir_filter filter_horizontal, stbir_filter filter_vertical,
stbir_colorspace space, void *alloc_context);
STBIRDEF int stbir_resize_subpixel(const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
stbir_datatype datatype,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
stbir_filter filter_horizontal, stbir_filter filter_vertical,
stbir_colorspace space, void *alloc_context,
float x_scale, float y_scale,
float x_offset, float y_offset);
STBIRDEF int stbir_resize_region( const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
stbir_datatype datatype,
int num_channels, int alpha_channel, int flags,
stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
stbir_filter filter_horizontal, stbir_filter filter_vertical,
stbir_colorspace space, void *alloc_context,
float s0, float t0, float s1, float t1);
// (s0, t0) & (s1, t1) are the top-left and bottom right corner (uv addressing style: [0, 1]x[0, 1]) of a region of the input image to use.
//
//
//// end header file /////////////////////////////////////////////////////
#endif // STBIR_INCLUDE_STB_IMAGE_RESIZE_H
#ifdef STB_IMAGE_RESIZE_IMPLEMENTATION
#ifndef STBIR_ASSERT
#include <assert.h>
#define STBIR_ASSERT(x) assert(x)
#endif
// For memset
#include <string.h>
#include <math.h>
#ifndef STBIR_MALLOC
#include <stdlib.h>
// use comma operator to evaluate c, to avoid "unused parameter" warnings
#define STBIR_MALLOC(size,c) ((void)(c), malloc(size))
#define STBIR_FREE(ptr,c) ((void)(c), free(ptr))
#endif
#ifndef _MSC_VER
#ifdef __cplusplus
#define stbir__inline inline
#else
#define stbir__inline
#endif
#else
#define stbir__inline __forceinline
#endif
// should produce compiler error if size is wrong
typedef unsigned char stbir__validate_uint32[sizeof(stbir_uint32) == 4 ? 1 : -1];
#ifdef _MSC_VER
#define STBIR__NOTUSED(v) (void)(v)
#else
#define STBIR__NOTUSED(v) (void)sizeof(v)
#endif
#define STBIR__ARRAY_SIZE(a) (sizeof((a))/sizeof((a)[0]))
#ifndef STBIR_DEFAULT_FILTER_UPSAMPLE
#define STBIR_DEFAULT_FILTER_UPSAMPLE STBIR_FILTER_CATMULLROM
#endif
#ifndef STBIR_DEFAULT_FILTER_DOWNSAMPLE
#define STBIR_DEFAULT_FILTER_DOWNSAMPLE STBIR_FILTER_MITCHELL
#endif
#ifndef STBIR_PROGRESS_REPORT
#define STBIR_PROGRESS_REPORT(float_0_to_1)
#endif
#ifndef STBIR_MAX_CHANNELS
#define STBIR_MAX_CHANNELS 64
#endif
#if STBIR_MAX_CHANNELS > 65536
#error "Too many channels; STBIR_MAX_CHANNELS must be no more than 65536."
// because we store the indices in 16-bit variables
#endif
// This value is added to alpha just before premultiplication to avoid
// zeroing out color values. It is equivalent to 2^-80. If you don't want
// that behavior (it may interfere if you have floating point images with
// very small alpha values) then you can define STBIR_NO_ALPHA_EPSILON to
// disable it.
#ifndef STBIR_ALPHA_EPSILON
#define STBIR_ALPHA_EPSILON ((float)1 / (1 << 20) / (1 << 20) / (1 << 20) / (1 << 20))
#endif
#ifdef _MSC_VER
#define STBIR__UNUSED_PARAM(v) (void)(v)
#else
#define STBIR__UNUSED_PARAM(v) (void)sizeof(v)
#endif
// must match stbir_datatype
static unsigned char stbir__type_size[] = {
1, // STBIR_TYPE_UINT8
2, // STBIR_TYPE_UINT16
4, // STBIR_TYPE_UINT32
4, // STBIR_TYPE_FLOAT
};
// Kernel function centered at 0
typedef float (stbir__kernel_fn)(float x, float scale);
typedef float (stbir__support_fn)(float scale);
typedef struct
{
stbir__kernel_fn* kernel;
stbir__support_fn* support;
} stbir__filter_info;
// When upsampling, the contributors are which source pixels contribute.
// When downsampling, the contributors are which destination pixels are contributed to.
typedef struct
{
int n0; // First contributing pixel
int n1; // Last contributing pixel
} stbir__contributors;
typedef struct
{
const void* input_data;
int input_w;
int input_h;
int input_stride_bytes;
void* output_data;
int output_w;
int output_h;
int output_stride_bytes;
float s0, t0, s1, t1;
float horizontal_shift; // Units: output pixels
float vertical_shift; // Units: output pixels
float horizontal_scale;
float vertical_scale;
int channels;
int alpha_channel;
stbir_uint32 flags;
stbir_datatype type;
stbir_filter horizontal_filter;
stbir_filter vertical_filter;
stbir_edge edge_horizontal;
stbir_edge edge_vertical;
stbir_colorspace colorspace;
stbir__contributors* horizontal_contributors;
float* horizontal_coefficients;
stbir__contributors* vertical_contributors;
float* vertical_coefficients;
int decode_buffer_pixels;
float* decode_buffer;
float* horizontal_buffer;
// cache these because ceil/floor are inexplicably showing up in profile
int horizontal_coefficient_width;
int vertical_coefficient_width;
int horizontal_filter_pixel_width;
int vertical_filter_pixel_width;
int horizontal_filter_pixel_margin;
int vertical_filter_pixel_margin;
int horizontal_num_contributors;
int vertical_num_contributors;
int ring_buffer_length_bytes; // The length of an individual entry in the ring buffer. The total number of ring buffers is stbir__get_filter_pixel_width(filter)
int ring_buffer_num_entries; // Total number of entries in the ring buffer.
int ring_buffer_first_scanline;
int ring_buffer_last_scanline;
int ring_buffer_begin_index; // first_scanline is at this index in the ring buffer
float* ring_buffer;
float* encode_buffer; // A temporary buffer to store floats so we don't lose precision while we do multiply-adds.
int horizontal_contributors_size;
int horizontal_coefficients_size;
int vertical_contributors_size;
int vertical_coefficients_size;
int decode_buffer_size;
int horizontal_buffer_size;
int ring_buffer_size;
int encode_buffer_size;
} stbir__info;
static const float stbir__max_uint8_as_float = 255.0f;
static const float stbir__max_uint16_as_float = 65535.0f;
static const double stbir__max_uint32_as_float = 4294967295.0;
static stbir__inline int stbir__min(int a, int b)
{
return a < b ? a : b;
}
static stbir__inline float stbir__saturate(float x)
{
if (x < 0)
return 0;
if (x > 1)
return 1;
return x;
}
#ifdef STBIR_SATURATE_INT
static stbir__inline stbir_uint8 stbir__saturate8(int x)
{
if ((unsigned int) x <= 255)
return x;
if (x < 0)
return 0;
return 255;
}
static stbir__inline stbir_uint16 stbir__saturate16(int x)
{
if ((unsigned int) x <= 65535)
return x;
if (x < 0)
return 0;
return 65535;
}
#endif
static float stbir__srgb_uchar_to_linear_float[256] = {
0.000000f, 0.000304f, 0.000607f, 0.000911f, 0.001214f, 0.001518f, 0.001821f, 0.002125f, 0.002428f, 0.002732f, 0.003035f,
0.003347f, 0.003677f, 0.004025f, 0.004391f, 0.004777f, 0.005182f, 0.005605f, 0.006049f, 0.006512f, 0.006995f, 0.007499f,
0.008023f, 0.008568f, 0.009134f, 0.009721f, 0.010330f, 0.010960f, 0.011612f, 0.012286f, 0.012983f, 0.013702f, 0.014444f,
0.015209f, 0.015996f, 0.016807f, 0.017642f, 0.018500f, 0.019382f, 0.020289f, 0.021219f, 0.022174f, 0.023153f, 0.024158f,
0.025187f, 0.026241f, 0.027321f, 0.028426f, 0.029557f, 0.030713f, 0.031896f, 0.033105f, 0.034340f, 0.035601f, 0.036889f,
0.038204f, 0.039546f, 0.040915f, 0.042311f, 0.043735f, 0.045186f, 0.046665f, 0.048172f, 0.049707f, 0.051269f, 0.052861f,
0.054480f, 0.056128f, 0.057805f, 0.059511f, 0.061246f, 0.063010f, 0.064803f, 0.066626f, 0.068478f, 0.070360f, 0.072272f,
0.074214f, 0.076185f, 0.078187f, 0.080220f, 0.082283f, 0.084376f, 0.086500f, 0.088656f, 0.090842f, 0.093059f, 0.095307f,
0.097587f, 0.099899f, 0.102242f, 0.104616f, 0.107023f, 0.109462f, 0.111932f, 0.114435f, 0.116971f, 0.119538f, 0.122139f,
0.124772f, 0.127438f, 0.130136f, 0.132868f, 0.135633f, 0.138432f, 0.141263f, 0.144128f, 0.147027f, 0.149960f, 0.152926f,
0.155926f, 0.158961f, 0.162029f, 0.165132f, 0.168269f, 0.171441f, 0.174647f, 0.177888f, 0.181164f, 0.184475f, 0.187821f,
0.191202f, 0.194618f, 0.198069f, 0.201556f, 0.205079f, 0.208637f, 0.212231f, 0.215861f, 0.219526f, 0.223228f, 0.226966f,
0.230740f, 0.234551f, 0.238398f, 0.242281f, 0.246201f, 0.250158f, 0.254152f, 0.258183f, 0.262251f, 0.266356f, 0.270498f,
0.274677f, 0.278894f, 0.283149f, 0.287441f, 0.291771f, 0.296138f, 0.300544f, 0.304987f, 0.309469f, 0.313989f, 0.318547f,
0.323143f, 0.327778f, 0.332452f, 0.337164f, 0.341914f, 0.346704f, 0.351533f, 0.356400f, 0.361307f, 0.366253f, 0.371238f,
0.376262f, 0.381326f, 0.386430f, 0.391573f, 0.396755f, 0.401978f, 0.407240f, 0.412543f, 0.417885f, 0.423268f, 0.428691f,
0.434154f, 0.439657f, 0.445201f, 0.450786f, 0.456411f, 0.462077f, 0.467784f, 0.473532f, 0.479320f, 0.485150f, 0.491021f,
0.496933f, 0.502887f, 0.508881f, 0.514918f, 0.520996f, 0.527115f, 0.533276f, 0.539480f, 0.545725f, 0.552011f, 0.558340f,
0.564712f, 0.571125f, 0.577581f, 0.584078f, 0.590619f, 0.597202f, 0.603827f, 0.610496f, 0.617207f, 0.623960f, 0.630757f,
0.637597f, 0.644480f, 0.651406f, 0.658375f, 0.665387f, 0.672443f, 0.679543f, 0.686685f, 0.693872f, 0.701102f, 0.708376f,
0.715694f, 0.723055f, 0.730461f, 0.737911f, 0.745404f, 0.752942f, 0.760525f, 0.768151f, 0.775822f, 0.783538f, 0.791298f,
0.799103f, 0.806952f, 0.814847f, 0.822786f, 0.830770f, 0.838799f, 0.846873f, 0.854993f, 0.863157f, 0.871367f, 0.879622f,
0.887923f, 0.896269f, 0.904661f, 0.913099f, 0.921582f, 0.930111f, 0.938686f, 0.947307f, 0.955974f, 0.964686f, 0.973445f,
0.982251f, 0.991102f, 1.0f
};
static float stbir__srgb_to_linear(float f)
{
if (f <= 0.04045f)
return f / 12.92f;
else
return (float)pow((f + 0.055f) / 1.055f, 2.4f);
}
static float stbir__linear_to_srgb(float f)
{
if (f <= 0.0031308f)
return f * 12.92f;
else
return 1.055f * (float)pow(f, 1 / 2.4f) - 0.055f;
}
#ifndef STBIR_NON_IEEE_FLOAT
// From https://gist.github.com/rygorous/2203834
typedef union
{
stbir_uint32 u;
float f;
} stbir__FP32;
static const stbir_uint32 fp32_to_srgb8_tab4[104] = {
0x0073000d, 0x007a000d, 0x0080000d, 0x0087000d, 0x008d000d, 0x0094000d, 0x009a000d, 0x00a1000d,
0x00a7001a, 0x00b4001a, 0x00c1001a, 0x00ce001a, 0x00da001a, 0x00e7001a, 0x00f4001a, 0x0101001a,
0x010e0033, 0x01280033, 0x01410033, 0x015b0033, 0x01750033, 0x018f0033, 0x01a80033, 0x01c20033,
0x01dc0067, 0x020f0067, 0x02430067, 0x02760067, 0x02aa0067, 0x02dd0067, 0x03110067, 0x03440067,
0x037800ce, 0x03df00ce, 0x044600ce, 0x04ad00ce, 0x051400ce, 0x057b00c5, 0x05dd00bc, 0x063b00b5,
0x06970158, 0x07420142, 0x07e30130, 0x087b0120, 0x090b0112, 0x09940106, 0x0a1700fc, 0x0a9500f2,
0x0b0f01cb, 0x0bf401ae, 0x0ccb0195, 0x0d950180, 0x0e56016e, 0x0f0d015e, 0x0fbc0150, 0x10630143,
0x11070264, 0x1238023e, 0x1357021d, 0x14660201, 0x156601e9, 0x165a01d3, 0x174401c0, 0x182401af,
0x18fe0331, 0x1a9602fe, 0x1c1502d2, 0x1d7e02ad, 0x1ed4028d, 0x201a0270, 0x21520256, 0x227d0240,
0x239f0443, 0x25c003fe, 0x27bf03c4, 0x29a10392, 0x2b6a0367, 0x2d1d0341, 0x2ebe031f, 0x304d0300,
0x31d105b0, 0x34a80555, 0x37520507, 0x39d504c5, 0x3c37048b, 0x3e7c0458, 0x40a8042a, 0x42bd0401,
0x44c20798, 0x488e071e, 0x4c1c06b6, 0x4f76065d, 0x52a50610, 0x55ac05cc, 0x5892058f, 0x5b590559,
0x5e0c0a23, 0x631c0980, 0x67db08f6, 0x6c55087f, 0x70940818, 0x74a007bd, 0x787d076c, 0x7c330723,
};
static stbir_uint8 stbir__linear_to_srgb_uchar(float in)
{
static const stbir__FP32 almostone = { 0x3f7fffff }; // 1-eps
static const stbir__FP32 minval = { (127-13) << 23 };
stbir_uint32 tab,bias,scale,t;
stbir__FP32 f;
// Clamp to [2^(-13), 1-eps]; these two values map to 0 and 1, respectively.
// The tests are carefully written so that NaNs map to 0, same as in the reference
// implementation.
if (!(in > minval.f)) // written this way to catch NaNs
in = minval.f;
if (in > almostone.f)
in = almostone.f;
// Do the table lookup and unpack bias, scale
f.f = in;
tab = fp32_to_srgb8_tab4[(f.u - minval.u) >> 20];
bias = (tab >> 16) << 9;
scale = tab & 0xffff;
// Grab next-highest mantissa bits and perform linear interpolation
t = (f.u >> 12) & 0xff;
return (unsigned char) ((bias + scale*t) >> 16);
}
#else
// sRGB transition values, scaled by 1<<28
static int stbir__srgb_offset_to_linear_scaled[256] =
{
0, 40738, 122216, 203693, 285170, 366648, 448125, 529603,
611080, 692557, 774035, 855852, 942009, 1033024, 1128971, 1229926,
1335959, 1447142, 1563542, 1685229, 1812268, 1944725, 2082664, 2226148,
2375238, 2529996, 2690481, 2856753, 3028870, 3206888, 3390865, 3580856,
3776916, 3979100, 4187460, 4402049, 4622919, 4850123, 5083710, 5323731,
5570236, 5823273, 6082892, 6349140, 6622065, 6901714, 7188133, 7481369,
7781466, 8088471, 8402427, 8723380, 9051372, 9386448, 9728650, 10078021,
10434603, 10798439, 11169569, 11548036, 11933879, 12327139, 12727857, 13136073,
13551826, 13975156, 14406100, 14844697, 15290987, 15745007, 16206795, 16676389,
17153826, 17639142, 18132374, 18633560, 19142734, 19659934, 20185196, 20718552,
21260042, 21809696, 22367554, 22933648, 23508010, 24090680, 24681686, 25281066,
25888850, 26505076, 27129772, 27762974, 28404716, 29055026, 29713942, 30381490,
31057708, 31742624, 32436272, 33138682, 33849884, 34569912, 35298800, 36036568,
36783260, 37538896, 38303512, 39077136, 39859796, 40651528, 41452360, 42262316,
43081432, 43909732, 44747252, 45594016, 46450052, 47315392, 48190064, 49074096,
49967516, 50870356, 51782636, 52704392, 53635648, 54576432, 55526772, 56486700,
57456236, 58435408, 59424248, 60422780, 61431036, 62449032, 63476804, 64514376,
65561776, 66619028, 67686160, 68763192, 69850160, 70947088, 72053992, 73170912,
74297864, 75434880, 76581976, 77739184, 78906536, 80084040, 81271736, 82469648,
83677792, 84896192, 86124888, 87363888, 88613232, 89872928, 91143016, 92423512,
93714432, 95015816, 96327688, 97650056, 98982952, 100326408, 101680440, 103045072,
104420320, 105806224, 107202800, 108610064, 110028048, 111456776, 112896264, 114346544,
115807632, 117279552, 118762328, 120255976, 121760536, 123276016, 124802440, 126339832,
127888216, 129447616, 131018048, 132599544, 134192112, 135795792, 137410592, 139036528,
140673648, 142321952, 143981456, 145652208, 147334208, 149027488, 150732064, 152447968,
154175200, 155913792, 157663776, 159425168, 161197984, 162982240, 164777968, 166585184,
168403904, 170234160, 172075968, 173929344, 175794320, 177670896, 179559120, 181458992,
183370528, 185293776, 187228736, 189175424, 191133888, 193104112, 195086128, 197079968,
199085648, 201103184, 203132592, 205173888, 207227120, 209292272, 211369392, 213458480,
215559568, 217672656, 219797792, 221934976, 224084240, 226245600, 228419056, 230604656,
232802400, 235012320, 237234432, 239468736, 241715280, 243974080, 246245120, 248528464,
250824112, 253132064, 255452368, 257785040, 260130080, 262487520, 264857376, 267239664,
};
static stbir_uint8 stbir__linear_to_srgb_uchar(float f)
{
int x = (int) (f * (1 << 28)); // has headroom so you don't need to clamp
int v = 0;
int i;
// Refine the guess with a short binary search.
i = v + 128; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 64; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 32; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 16; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 8; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 4; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 2; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
i = v + 1; if (x >= stbir__srgb_offset_to_linear_scaled[i]) v = i;
return (stbir_uint8) v;
}
#endif
static float stbir__filter_trapezoid(float x, float scale)
{
float halfscale = scale / 2;
float t = 0.5f + halfscale;
STBIR_ASSERT(scale <= 1);
x = (float)fabs(x);
if (x >= t)
return 0;
else
{
float r = 0.5f - halfscale;
if (x <= r)
return 1;
else
return (t - x) / scale;
}
}
static float stbir__support_trapezoid(float scale)
{
STBIR_ASSERT(scale <= 1);
return 0.5f + scale / 2;
}
static float stbir__filter_triangle(float x, float s)
{
STBIR__UNUSED_PARAM(s);
x = (float)fabs(x);
if (x <= 1.0f)
return 1 - x;
else
return 0;
}
static float stbir__filter_cubic(float x, float s)
{
STBIR__UNUSED_PARAM(s);
x = (float)fabs(x);
if (x < 1.0f)
return (4 + x*x*(3*x - 6))/6;
else if (x < 2.0f)
return (8 + x*(-12 + x*(6 - x)))/6;
return (0.0f);
}
static float stbir__filter_catmullrom(float x, float s)
{
STBIR__UNUSED_PARAM(s);
x = (float)fabs(x);
if (x < 1.0f)
return 1 - x*x*(2.5f - 1.5f*x);
else if (x < 2.0f)
return 2 - x*(4 + x*(0.5f*x - 2.5f));
return (0.0f);
}
static float stbir__filter_mitchell(float x, float s)
{
STBIR__UNUSED_PARAM(s);
x = (float)fabs(x);
if (x < 1.0f)
return (16 + x*x*(21 * x - 36))/18;
else if (x < 2.0f)
return (32 + x*(-60 + x*(36 - 7*x)))/18;
return (0.0f);
}
static float stbir__support_zero(float s)
{
STBIR__UNUSED_PARAM(s);
return 0;
}
static float stbir__support_one(float s)
{
STBIR__UNUSED_PARAM(s);
return 1;
}
static float stbir__support_two(float s)
{
STBIR__UNUSED_PARAM(s);
return 2;
}
static stbir__filter_info stbir__filter_info_table[] = {
{ NULL, stbir__support_zero },
{ stbir__filter_trapezoid, stbir__support_trapezoid },
{ stbir__filter_triangle, stbir__support_one },
{ stbir__filter_cubic, stbir__support_two },
{ stbir__filter_catmullrom, stbir__support_two },
{ stbir__filter_mitchell, stbir__support_two },
};
stbir__inline static int stbir__use_upsampling(float ratio)
{
return ratio > 1;
}
stbir__inline static int stbir__use_width_upsampling(stbir__info* stbir_info)
{
return stbir__use_upsampling(stbir_info->horizontal_scale);
}
stbir__inline static int stbir__use_height_upsampling(stbir__info* stbir_info)
{
return stbir__use_upsampling(stbir_info->vertical_scale);
}
// This is the maximum number of input samples that can affect an output sample
// with the given filter
static int stbir__get_filter_pixel_width(stbir_filter filter, float scale)
{
STBIR_ASSERT(filter != 0);
STBIR_ASSERT(filter < STBIR__ARRAY_SIZE(stbir__filter_info_table));
if (stbir__use_upsampling(scale))
return (int)ceil(stbir__filter_info_table[filter].support(1/scale) * 2);
else
return (int)ceil(stbir__filter_info_table[filter].support(scale) * 2 / scale);
}
// This is how much to expand buffers to account for filters seeking outside
// the image boundaries.
static int stbir__get_filter_pixel_margin(stbir_filter filter, float scale)
{
return stbir__get_filter_pixel_width(filter, scale) / 2;
}
static int stbir__get_coefficient_width(stbir_filter filter, float scale)
{
if (stbir__use_upsampling(scale))
return (int)ceil(stbir__filter_info_table[filter].support(1 / scale) * 2);
else
return (int)ceil(stbir__filter_info_table[filter].support(scale) * 2);
}
static int stbir__get_contributors(float scale, stbir_filter filter, int input_size, int output_size)
{
if (stbir__use_upsampling(scale))
return output_size;
else
return (input_size + stbir__get_filter_pixel_margin(filter, scale) * 2);
}
static int stbir__get_total_horizontal_coefficients(stbir__info* info)
{
return info->horizontal_num_contributors
* stbir__get_coefficient_width (info->horizontal_filter, info->horizontal_scale);
}
static int stbir__get_total_vertical_coefficients(stbir__info* info)
{
return info->vertical_num_contributors
* stbir__get_coefficient_width (info->vertical_filter, info->vertical_scale);
}
static stbir__contributors* stbir__get_contributor(stbir__contributors* contributors, int n)
{
return &contributors[n];
}
// For perf reasons this code is duplicated in stbir__resample_horizontal_upsample/downsample,
// if you change it here change it there too.
static float* stbir__get_coefficient(float* coefficients, stbir_filter filter, float scale, int n, int c)
{
int width = stbir__get_coefficient_width(filter, scale);
return &coefficients[width*n + c];
}
static int stbir__edge_wrap_slow(stbir_edge edge, int n, int max)
{
switch (edge)
{
case STBIR_EDGE_ZERO:
return 0; // we'll decode the wrong pixel here, and then overwrite with 0s later
case STBIR_EDGE_CLAMP:
if (n < 0)
return 0;
if (n >= max)
return max - 1;
return n; // NOTREACHED
case STBIR_EDGE_REFLECT:
{
if (n < 0)
{
if (n < max)
return -n;
else
return max - 1;
}
if (n >= max)
{
int max2 = max * 2;
if (n >= max2)
return 0;
else
return max2 - n - 1;
}
return n; // NOTREACHED
}
case STBIR_EDGE_WRAP:
if (n >= 0)
return (n % max);
else
{
int m = (-n) % max;
if (m != 0)
m = max - m;
return (m);
}
// NOTREACHED
default:
STBIR_ASSERT(!"Unimplemented edge type");
return 0;
}
}
stbir__inline static int stbir__edge_wrap(stbir_edge edge, int n, int max)