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427 lines
21 KiB
C++
427 lines
21 KiB
C++
// SPDX-FileCopyrightText: Jorge L Rodriguez
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// SPDX-License-Identifier: MIT
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/* stb_image_resize - v0.97 - public domain image resizing
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by Jorge L Rodriguez (@VinoBS) - 2014
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http://github.com/nothings/stb
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Written with emphasis on usability, portability, and efficiency. (No
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SIMD or threads, so it be easily outperformed by libs that use those.)
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Only scaling and translation is supported, no rotations or shears.
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Easy API downsamples w/Mitchell filter, upsamples w/cubic interpolation.
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COMPILING & LINKING
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In one C/C++ file that #includes this file, do this:
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#define STB_IMAGE_RESIZE_IMPLEMENTATION
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before the #include. That will create the implementation in that file.
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QUICKSTART
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stbir_resize_uint8( input_pixels , in_w , in_h , 0,
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output_pixels, out_w, out_h, 0, num_channels)
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stbir_resize_float(...)
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stbir_resize_uint8_srgb( input_pixels , in_w , in_h , 0,
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output_pixels, out_w, out_h, 0,
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num_channels , alpha_chan , 0)
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stbir_resize_uint8_srgb_edgemode(
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input_pixels , in_w , in_h , 0,
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output_pixels, out_w, out_h, 0,
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num_channels , alpha_chan , 0, STBIR_EDGE_CLAMP)
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// WRAP/REFLECT/ZERO
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FULL API
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See the "header file" section of the source for API documentation.
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ADDITIONAL DOCUMENTATION
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SRGB & FLOATING POINT REPRESENTATION
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The sRGB functions presume IEEE floating point. If you do not have
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IEEE floating point, define STBIR_NON_IEEE_FLOAT. This will use
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a slower implementation.
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MEMORY ALLOCATION
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The resize functions here perform a single memory allocation using
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malloc. To control the memory allocation, before the #include that
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triggers the implementation, do:
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#define STBIR_MALLOC(size,context) ...
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#define STBIR_FREE(ptr,context) ...
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Each resize function makes exactly one call to malloc/free, so to use
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temp memory, store the temp memory in the context and return that.
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ASSERT
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Define STBIR_ASSERT(boolval) to override assert() and not use assert.h
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OPTIMIZATION
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Define STBIR_SATURATE_INT to compute clamp values in-range using
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integer operations instead of float operations. This may be faster
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on some platforms.
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DEFAULT FILTERS
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For functions which don't provide explicit control over what filters
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to use, you can change the compile-time defaults with
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#define STBIR_DEFAULT_FILTER_UPSAMPLE STBIR_FILTER_something
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#define STBIR_DEFAULT_FILTER_DOWNSAMPLE STBIR_FILTER_something
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See stbir_filter in the header-file section for the list of filters.
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NEW FILTERS
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A number of 1D filter kernels are used. For a list of
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supported filters see the stbir_filter enum. To add a new filter,
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write a filter function and add it to stbir__filter_info_table.
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PROGRESS
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For interactive use with slow resize operations, you can install
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a progress-report callback:
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#define STBIR_PROGRESS_REPORT(val) some_func(val)
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The parameter val is a float which goes from 0 to 1 as progress is made.
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For example:
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static void my_progress_report(float progress);
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#define STBIR_PROGRESS_REPORT(val) my_progress_report(val)
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#define STB_IMAGE_RESIZE_IMPLEMENTATION
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#include "stb_image_resize.h"
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static void my_progress_report(float progress)
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{
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printf("Progress: %f%%\n", progress*100);
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}
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MAX CHANNELS
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If your image has more than 64 channels, define STBIR_MAX_CHANNELS
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to the max you'll have.
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ALPHA CHANNEL
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Most of the resizing functions provide the ability to control how
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the alpha channel of an image is processed. The important things
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to know about this:
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1. The best mathematically-behaved version of alpha to use is
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called "premultiplied alpha", in which the other color channels
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have had the alpha value multiplied in. If you use premultiplied
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alpha, linear filtering (such as image resampling done by this
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library, or performed in texture units on GPUs) does the "right
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thing". While premultiplied alpha is standard in the movie CGI
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industry, it is still uncommon in the videogame/real-time world.
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If you linearly filter non-premultiplied alpha, strange effects
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occur. (For example, the 50/50 average of 99% transparent bright green
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and 1% transparent black produces 50% transparent dark green when
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non-premultiplied, whereas premultiplied it produces 50%
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transparent near-black. The former introduces green energy
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that doesn't exist in the source image.)
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2. Artists should not edit premultiplied-alpha images; artists
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want non-premultiplied alpha images. Thus, art tools generally output
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non-premultiplied alpha images.
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3. You will get best results in most cases by converting images
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to premultiplied alpha before processing them mathematically.
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4. If you pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED, the
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resizer does not do anything special for the alpha channel;
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it is resampled identically to other channels. This produces
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the correct results for premultiplied-alpha images, but produces
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less-than-ideal results for non-premultiplied-alpha images.
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5. If you do not pass the flag STBIR_FLAG_ALPHA_PREMULTIPLIED,
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then the resizer weights the contribution of input pixels
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based on their alpha values, or, equivalently, it multiplies
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the alpha value into the color channels, resamples, then divides
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by the resultant alpha value. Input pixels which have alpha=0 do
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not contribute at all to output pixels unless _all_ of the input
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pixels affecting that output pixel have alpha=0, in which case
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the result for that pixel is the same as it would be without
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STBIR_FLAG_ALPHA_PREMULTIPLIED. However, this is only true for
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input images in integer formats. For input images in float format,
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input pixels with alpha=0 have no effect, and output pixels
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which have alpha=0 will be 0 in all channels. (For float images,
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you can manually achieve the same result by adding a tiny epsilon
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value to the alpha channel of every image, and then subtracting
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or clamping it at the end.)
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6. You can suppress the behavior described in #5 and make
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all-0-alpha pixels have 0 in all channels by #defining
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STBIR_NO_ALPHA_EPSILON.
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7. You can separately control whether the alpha channel is
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interpreted as linear or affected by the colorspace. By default
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it is linear; you almost never want to apply the colorspace.
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(For example, graphics hardware does not apply sRGB conversion
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to the alpha channel.)
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CONTRIBUTORS
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Jorge L Rodriguez: Implementation
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Sean Barrett: API design, optimizations
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Aras Pranckevicius: bugfix
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Nathan Reed: warning fixes
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REVISIONS
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0.97 (2020-02-02) fixed warning
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0.96 (2019-03-04) fixed warnings
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0.95 (2017-07-23) fixed warnings
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0.94 (2017-03-18) fixed warnings
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0.93 (2017-03-03) fixed bug with certain combinations of heights
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0.92 (2017-01-02) fix integer overflow on large (>2GB) images
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0.91 (2016-04-02) fix warnings; fix handling of subpixel regions
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0.90 (2014-09-17) first released version
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LICENSE
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See end of file for license information.
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TODO
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Don't decode all of the image data when only processing a partial tile
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Don't use full-width decode buffers when only processing a partial tile
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When processing wide images, break processing into tiles so data fits in L1 cache
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Installable filters?
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Resize that respects alpha test coverage
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(Reference code: FloatImage::alphaTestCoverage and FloatImage::scaleAlphaToCoverage:
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https://code.google.com/p/nvidia-texture-tools/source/browse/trunk/src/nvimage/FloatImage.cpp )
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*/
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#ifndef STBIR_INCLUDE_STB_IMAGE_RESIZE_H
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#define STBIR_INCLUDE_STB_IMAGE_RESIZE_H
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#ifdef _MSC_VER
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typedef unsigned char stbir_uint8;
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typedef unsigned short stbir_uint16;
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typedef unsigned int stbir_uint32;
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#else
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#include <stdint.h>
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typedef uint8_t stbir_uint8;
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typedef uint16_t stbir_uint16;
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typedef uint32_t stbir_uint32;
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#endif
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#ifndef STBIRDEF
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#ifdef STB_IMAGE_RESIZE_STATIC
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#define STBIRDEF static
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#else
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#ifdef __cplusplus
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#define STBIRDEF extern "C"
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#else
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#define STBIRDEF extern
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#endif
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#endif
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#endif
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//////////////////////////////////////////////////////////////////////////////
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//
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// Easy-to-use API:
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//
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// * "input pixels" points to an array of image data with 'num_channels' channels (e.g. RGB=3, RGBA=4)
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// * input_w is input image width (x-axis), input_h is input image height (y-axis)
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// * stride is the offset between successive rows of image data in memory, in bytes. you can
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// specify 0 to mean packed continuously in memory
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// * alpha channel is treated identically to other channels.
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// * colorspace is linear or sRGB as specified by function name
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// * returned result is 1 for success or 0 in case of an error.
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// #define STBIR_ASSERT() to trigger an assert on parameter validation errors.
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// * Memory required grows approximately linearly with input and output size, but with
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// discontinuities at input_w == output_w and input_h == output_h.
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// * These functions use a "default" resampling filter defined at compile time. To change the filter,
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// you can change the compile-time defaults by #defining STBIR_DEFAULT_FILTER_UPSAMPLE
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// and STBIR_DEFAULT_FILTER_DOWNSAMPLE, or you can use the medium-complexity API.
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STBIRDEF int stbir_resize_uint8( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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int num_channels);
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STBIRDEF int stbir_resize_float( const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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float *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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int num_channels);
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// The following functions interpret image data as gamma-corrected sRGB.
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// Specify STBIR_ALPHA_CHANNEL_NONE if you have no alpha channel,
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// or otherwise provide the index of the alpha channel. Flags value
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// of 0 will probably do the right thing if you're not sure what
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// the flags mean.
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#define STBIR_ALPHA_CHANNEL_NONE -1
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// Set this flag if your texture has premultiplied alpha. Otherwise, stbir will
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// use alpha-weighted resampling (effectively premultiplying, resampling,
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// then unpremultiplying).
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#define STBIR_FLAG_ALPHA_PREMULTIPLIED (1 << 0)
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// The specified alpha channel should be handled as gamma-corrected value even
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// when doing sRGB operations.
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#define STBIR_FLAG_ALPHA_USES_COLORSPACE (1 << 1)
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STBIRDEF int stbir_resize_uint8_srgb(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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int num_channels, int alpha_channel, int flags);
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typedef enum
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{
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STBIR_EDGE_CLAMP = 1,
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STBIR_EDGE_REFLECT = 2,
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STBIR_EDGE_WRAP = 3,
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STBIR_EDGE_ZERO = 4,
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} stbir_edge;
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// This function adds the ability to specify how requests to sample off the edge of the image are handled.
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STBIRDEF int stbir_resize_uint8_srgb_edgemode(const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_wrap_mode);
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//////////////////////////////////////////////////////////////////////////////
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//
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// Medium-complexity API
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//
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// This extends the easy-to-use API as follows:
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//
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// * Alpha-channel can be processed separately
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// * If alpha_channel is not STBIR_ALPHA_CHANNEL_NONE
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// * Alpha channel will not be gamma corrected (unless flags&STBIR_FLAG_GAMMA_CORRECT)
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// * Filters will be weighted by alpha channel (unless flags&STBIR_FLAG_ALPHA_PREMULTIPLIED)
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// * Filter can be selected explicitly
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// * uint16 image type
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// * sRGB colorspace available for all types
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// * context parameter for passing to STBIR_MALLOC
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typedef enum
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{
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STBIR_FILTER_DEFAULT = 0, // use same filter type that easy-to-use API chooses
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STBIR_FILTER_BOX = 1, // A trapezoid w/1-pixel wide ramps, same result as box for integer scale ratios
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STBIR_FILTER_TRIANGLE = 2, // On upsampling, produces same results as bilinear texture filtering
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STBIR_FILTER_CUBICBSPLINE = 3, // The cubic b-spline (aka Mitchell-Netrevalli with B=1,C=0), gaussian-esque
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STBIR_FILTER_CATMULLROM = 4, // An interpolating cubic spline
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STBIR_FILTER_MITCHELL = 5, // Mitchell-Netrevalli filter with B=1/3, C=1/3
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} stbir_filter;
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typedef enum
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{
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STBIR_COLORSPACE_LINEAR,
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STBIR_COLORSPACE_SRGB,
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STBIR_MAX_COLORSPACES,
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} stbir_colorspace;
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// The following functions are all identical except for the type of the image data
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STBIRDEF int stbir_resize_uint8_generic( const unsigned char *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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unsigned char *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
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void *alloc_context);
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STBIRDEF int stbir_resize_uint16_generic(const stbir_uint16 *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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stbir_uint16 *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
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void *alloc_context);
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STBIRDEF int stbir_resize_float_generic( const float *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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float *output_pixels , int output_w, int output_h, int output_stride_in_bytes,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_wrap_mode, stbir_filter filter, stbir_colorspace space,
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void *alloc_context);
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//////////////////////////////////////////////////////////////////////////////
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//
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// Full-complexity API
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//
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// This extends the medium API as follows:
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//
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// * uint32 image type
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// * not typesafe
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// * separate filter types for each axis
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// * separate edge modes for each axis
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// * can specify scale explicitly for subpixel correctness
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// * can specify image source tile using texture coordinates
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typedef enum
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{
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STBIR_TYPE_UINT8 ,
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STBIR_TYPE_UINT16,
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STBIR_TYPE_UINT32,
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STBIR_TYPE_FLOAT ,
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STBIR_MAX_TYPES
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} stbir_datatype;
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STBIRDEF int stbir_resize( const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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stbir_datatype datatype,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
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stbir_filter filter_horizontal, stbir_filter filter_vertical,
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stbir_colorspace space, void *alloc_context);
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STBIRDEF int stbir_resize_subpixel(const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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stbir_datatype datatype,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
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stbir_filter filter_horizontal, stbir_filter filter_vertical,
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stbir_colorspace space, void *alloc_context,
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float x_scale, float y_scale,
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float x_offset, float y_offset);
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STBIRDEF int stbir_resize_region( const void *input_pixels , int input_w , int input_h , int input_stride_in_bytes,
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void *output_pixels, int output_w, int output_h, int output_stride_in_bytes,
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stbir_datatype datatype,
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int num_channels, int alpha_channel, int flags,
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stbir_edge edge_mode_horizontal, stbir_edge edge_mode_vertical,
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stbir_filter filter_horizontal, stbir_filter filter_vertical,
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stbir_colorspace space, void *alloc_context,
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float s0, float t0, float s1, float t1);
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// (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.
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//
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//
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//// end header file /////////////////////////////////////////////////////
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#endif // STBIR_INCLUDE_STB_IMAGE_RESIZE_H
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/*
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------------------------------------------------------------------------------
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This software is available under 2 licenses -- choose whichever you prefer.
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------------------------------------------------------------------------------
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ALTERNATIVE A - MIT License
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Copyright (c) 2017 Sean Barrett
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do
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so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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------------------------------------------------------------------------------
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ALTERNATIVE B - Public Domain (www.unlicense.org)
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This is free and unencumbered software released into the public domain.
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Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
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software, either in source code form or as a compiled binary, for any purpose,
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commercial or non-commercial, and by any means.
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In jurisdictions that recognize copyright laws, the author or authors of this
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software dedicate any and all copyright interest in the software to the public
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domain. We make this dedication for the benefit of the public at large and to
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the detriment of our heirs and successors. We intend this dedication to be an
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overt act of relinquishment in perpetuity of all present and future rights to
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this software under copyright law.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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------------------------------------------------------------------------------
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*/
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