stb/stb_resample.h

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/* stb_resample - v0.1 - public domain image resampling
no warranty implied; use at your own risk
Do this:
#define STB_RESAMPLE_IMPLEMENTATION
before you include this file in *one* C or C++ file to create the implementation.
#define STBR_ASSERT(x) to avoid using assert.h.
Latest revisions:
See end of file for full revision history.
Initial implementation by Jorge L Rodriguez
*/
#ifndef STBR_INCLUDE_STB_RESAMPLE_H
#define STBR_INCLUDE_STB_RESAMPLE_H
// Basic usage:
// result = stbr_resize(input_data, input_w, input_h, 0, output_data, output_w, output_h, 0, channels, alpha_channel, STBR_TYPE_UINT8, STBR_FILTER_BILINEAR, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB);
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//
// input_data is your supplied texels.
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// output_data will be the resized texels. It should be of size output_w * output_h * input_components (or output_h * output_stride if you provided a stride.)
// If input_stride or output_stride is 0 (as in this example) the stride will be automatically calculated as width*components.
// Returned result is 1 for success or 0 in case of an error.
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typedef enum
{
STBR_FILTER_NEAREST = 1,
STBR_FILTER_LINEAR = 2,
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} stbr_filter;
typedef enum
{
STBR_EDGE_CLAMP = 1,
} stbr_edge;
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typedef enum
{
STBR_COLORSPACE_LINEAR = 1,
STBR_COLORSPACE_SRGB = 2,
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} stbr_colorspace;
typedef enum
{
STBR_TYPE_UINT8 = 1,
} stbr_type;
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typedef unsigned char stbr_uc;
typedef unsigned int stbr_size_t; // to avoid including a header for size_t
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#ifdef __cplusplus
extern "C" {
#endif
#ifdef STB_RESAMPLE_STATIC
#define STBRDEF static
#else
#define STBRDEF extern
#endif
//////////////////////////////////////////////////////////////////////////////
//
// PRIMARY API - resize an image
//
STBRDEF stbr_size_t stbr_calculate_memory(int input_w, int input_h, int input_stride_in_bytes,
int output_w, int output_h, int output_stride_in_bytes,
int channels, stbr_filter filter);
STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
void* output_data, int output_w, int output_h, int output_stride_in_bytes,
//int channels, int alpha_channel, stbr_type type, stbr_filter filter, stbr_edge edge, stbr_colorspace colorspace,
int channels, stbr_type type, stbr_filter filter, stbr_edge edge,
void* tempmem, stbr_size_t tempmem_size_in_bytes);
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#ifdef __cplusplus
}
#endif
//
//
//// end header file /////////////////////////////////////////////////////
#endif // STBR_INCLUDE_STB_RESAMPLE_H
#ifdef STB_RESIZE_IMPLEMENTATION
#ifndef STBR_ASSERT
#include <assert.h>
#define STBR_ASSERT(x) assert(x)
#endif
#ifdef STBR_DEBUG
#define STBR_DEBUG_ASSERT STBR_ASSERT
#else
#define STBR_DEBUG_ASSERT
#endif
// If you hit this it means I haven't done it yet.
#define STBR_UNIMPLEMENTED(x) STBR_ASSERT(!(x))
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#ifdef STBR_DEBUG_OVERWRITE_TEST
#include <string.h>
#endif
#include <math.h>
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#ifndef _MSC_VER
#ifdef __cplusplus
#define stbr_inline inline
#else
#define stbr_inline
#endif
#else
#define stbr_inline __forceinline
#endif
#ifdef _MSC_VER
typedef unsigned short stbr__uint16;
typedef signed short stbr__int16;
typedef unsigned int stbr__uint32;
typedef signed int stbr__int32;
#else
#include <stdint.h>
typedef uint16_t stbr__uint16;
typedef int16_t stbr__int16;
typedef uint32_t stbr__uint32;
typedef int32_t stbr__int32;
#endif
// should produce compiler error if size is wrong
typedef unsigned char stbr__validate_uint32[sizeof(stbr__uint32) == 4 ? 1 : -1];
#ifdef _MSC_VER
#define STBR_NOTUSED(v) (void)(v)
#else
#define STBR_NOTUSED(v) (void)sizeof(v)
#endif
#define STBR_ARRAY_SIZE(a) (sizeof((a))/sizeof((a)[0]))
// Kernel function centered at 0
typedef float (stbr__kernel_fn)(float x);
typedef struct
{
stbr__kernel_fn* kernel;
float support;
} stbr__filter_info;
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// When upsampling, the contributors are which source texels contribute.
// When downsampling, the contributors are which destination texels are contributed to.
typedef struct
{
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int n0; // First contributing texel
int n1; // Last contributing texel
} stbr__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;
int channels;
stbr_type type;
stbr_filter filter;
stbr_edge edge;
stbr__contributors* horizontal_contributors;
float* horizontal_coefficients;
stbr__contributors vertical_contributors;
float* vertical_coefficients;
int decode_buffer_texels;
float* decode_buffer;
float* horizontal_buffer;
int ring_buffer_length_bytes; // The length of an individual entry in the ring buffer. The total number of ring buffers is stbr__get_filter_texel_width(filter)
int ring_buffer_first_scanline;
int ring_buffer_last_scanline;
int ring_buffer_begin_index;
float* ring_buffer;
float* encode_buffer; // A temporary buffer to store floats so we don't lose precision while we do multiply-adds.
} stbr__info;
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static stbr_inline int stbr__min(int a, int b)
{
return a < b ? a : b;
}
static stbr_inline int stbr__max(int a, int b)
{
return a > b ? a : b;
}
static float stbr__filter_nearest(float x)
{
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if (fabs(x) <= 0.5)
return 1;
else
return 0;
}
static float stbr__filter_linear(float x)
{
x = (float)fabs(x);
if (x <= 1.0f)
return 1 - x;
else
return 0;
}
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static stbr__filter_info stbr__filter_info_table[] = {
{ NULL, 0.0f },
{ stbr__filter_nearest, 0.5f },
{ stbr__filter_linear, 1.0f },
};
stbr_inline static int stbr__use_width_upsampling_noinfo(int output_w, int input_w)
{
return output_w > input_w;
}
stbr_inline static int stbr__use_height_upsampling_noinfo(int output_h, int input_h)
{
return output_h > input_h;
}
stbr_inline static int stbr__use_width_upsampling(stbr__info* stbr_info)
{
return stbr__use_width_upsampling_noinfo(stbr_info->output_w, stbr_info->input_w);
}
stbr_inline static int stbr__use_height_upsampling(stbr__info* stbr_info)
{
return stbr__use_height_upsampling_noinfo(stbr_info->output_h, stbr_info->input_h);
}
// This is the maximum number of input samples that can affect an output sample
// with the given filter
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stbr_inline static int stbr__get_filter_texel_width(stbr_filter filter)
{
STBR_ASSERT(filter != 0);
STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
return (int)ceil(stbr__filter_info_table[filter].support * 2);
}
// This is how much to expand buffers to account for filters seeking outside
// the image boundaries.
stbr_inline static int stbr__get_filter_texel_margin(stbr_filter filter)
{
return stbr__get_filter_texel_width(filter) / 2;
}
stbr_inline static int stbr__get_horizontal_contributors(stbr_filter filter, int input_w, int output_w)
{
if (stbr__use_width_upsampling_noinfo(output_w, input_w))
return output_w;
else
return (input_w + stbr__get_filter_texel_margin(filter) * 2);
}
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stbr_inline static int stbr__get_total_coefficients(stbr_filter filter, int input_w, int output_w)
{
return stbr__get_horizontal_contributors(filter, input_w, output_w) * stbr__get_filter_texel_width(filter);
}
stbr_inline static stbr__contributors* stbr__get_contributor(stbr__info* stbr_info, int n)
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{
STBR_DEBUG_ASSERT(n >= 0 && n < stbr__get_horizontal_contributors(stbr_info->filter, stbr_info->input_w, stbr_info->output_w));
return &stbr_info->horizontal_contributors[n];
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}
stbr_inline static float* stbr__get_coefficient(stbr__info* stbr_info, int n, int c)
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{
return &stbr_info->horizontal_coefficients[stbr__get_filter_texel_width(stbr_info->filter)*n + c];
}
stbr_inline static int stbr__edge_wrap(stbr_edge edge, int n, int max)
{
STBR_UNIMPLEMENTED(edge != STBR_EDGE_CLAMP);
switch (edge)
{
default:
case STBR_EDGE_CLAMP:
if (n < 0)
return 0;
if (n >= max)
return max - 1;
return n;
}
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}
// What input texels contribute to this output texel?
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static void stbr__calculate_sample_range_upsample(int n, float out_filter_radius, float scale_ratio, int* in_first_texel, int* in_last_texel, float* in_center_of_out)
{
float out_texel_center = (float)n + 0.5f;
float out_texel_influence_lowerbound = out_texel_center - out_filter_radius;
float out_texel_influence_upperbound = out_texel_center + out_filter_radius;
float in_texel_influence_lowerbound = out_texel_influence_lowerbound / scale_ratio;
float in_texel_influence_upperbound = out_texel_influence_upperbound / scale_ratio;
*in_center_of_out = out_texel_center / scale_ratio;
*in_first_texel = (int)(floor(in_texel_influence_lowerbound + 0.5));
*in_last_texel = (int)(floor(in_texel_influence_upperbound - 0.5));
}
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// What output texels does this input texel contribute to?
static void stbr__calculate_sample_range_downsample(int n, float in_pixels_radius, float scale_ratio, int* out_first_texel, int* out_last_texel, float* out_center_of_in)
{
float in_texel_center = (float)n + 0.5f;
float in_texel_influence_lowerbound = in_texel_center - in_pixels_radius;
float in_texel_influence_upperbound = in_texel_center + in_pixels_radius;
float out_texel_influence_lowerbound = in_texel_influence_lowerbound * scale_ratio;
float out_texel_influence_upperbound = in_texel_influence_upperbound * scale_ratio;
*out_center_of_in = in_texel_center * scale_ratio;
*out_first_texel = (int)(floor(out_texel_influence_lowerbound + 0.5));
*out_last_texel = (int)(floor(out_texel_influence_upperbound - 0.5));
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}
static void stbr__calculate_coefficients_upsample(stbr__info* stbr_info, int in_first_texel, int in_last_texel, float in_center_of_out, stbr__contributors* contributor, float* coefficient_group)
{
int i;
float total_filter = 0;
float filter_scale;
stbr_filter filter = stbr_info->filter;
STBR_DEBUG_ASSERT(in_last_texel - in_first_texel <= stbr__get_filter_texel_width(filter));
STBR_DEBUG_ASSERT(in_last_texel < stbr__get_horizontal_contributors(stbr_info->filter, stbr_info->input_w, stbr_info->output_w));
contributor->n0 = in_first_texel;
contributor->n1 = in_last_texel;
for (i = 0; i <= in_last_texel - in_first_texel; i++)
{
float in_texel_center = (float)(i + in_first_texel) + 0.5f;
total_filter += coefficient_group[i] = stbr__filter_info_table[filter].kernel(in_center_of_out - in_texel_center);
}
STBR_DEBUG_ASSERT(total_filter > 0);
STBR_DEBUG_ASSERT(fabs(1 - total_filter) < 0.1f); // Make sure it's not way off.
// Make sure the sum of all coefficients is 1.
filter_scale = 1 / total_filter;
for (i = 0; i <= in_last_texel - in_first_texel; i++)
coefficient_group[i] *= filter_scale;
}
static void stbr__calculate_coefficients_downsample(stbr__info* stbr_info, float scale_ratio, int out_first_texel, int out_last_texel, float out_center_of_in, stbr__contributors* contributor, float* coefficient_group)
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{
int i;
stbr_filter filter = stbr_info->filter;
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STBR_DEBUG_ASSERT(out_last_texel - out_first_texel <= stbr__get_filter_texel_width(filter));
STBR_DEBUG_ASSERT(out_last_texel < stbr__get_horizontal_contributors(stbr_info->filter, stbr_info->input_w, stbr_info->output_w));
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contributor->n0 = out_first_texel;
contributor->n1 = out_last_texel;
for (i = 0; i <= out_last_texel - out_first_texel; i++)
{
float in_texel_center = (float)(i + out_first_texel) + 0.5f;
coefficient_group[i] = stbr__filter_info_table[filter].kernel(out_center_of_in - in_texel_center) * scale_ratio;
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}
}
// Each scan line uses the same kernel values so we should calculate the kernel
// values once and then we can use them for every scan line.
static void stbr__calculate_horizontal_filters(stbr__info* stbr_info)
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{
int n;
float scale_ratio = (float)stbr_info->output_w / stbr_info->input_w;
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int total_contributors = stbr__get_horizontal_contributors(stbr_info->filter, stbr_info->input_w, stbr_info->output_w);
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if (stbr__use_width_upsampling(stbr_info))
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{
float out_pixels_radius = stbr__filter_info_table[stbr_info->filter].support * scale_ratio;
// Looping through out texels
for (n = 0; n < total_contributors; n++)
{
float in_center_of_out; // Center of the current out texel in the in texel space
int in_first_texel, in_last_texel;
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stbr__calculate_sample_range_upsample(n, out_pixels_radius, scale_ratio, &in_first_texel, &in_last_texel, &in_center_of_out);
stbr__calculate_coefficients_upsample(stbr_info, in_first_texel, in_last_texel, in_center_of_out, stbr__get_contributor(stbr_info, n), stbr__get_coefficient(stbr_info, n, 0));
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}
}
else
{
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float in_pixels_radius = stbr__filter_info_table[stbr_info->filter].support / scale_ratio;
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// Looping through in texels
for (n = 0; n < total_contributors; n++)
{
float out_center_of_in; // Center of the current out texel in the in texel space
int out_first_texel, out_last_texel;
int n_adjusted = n - stbr__get_filter_texel_margin(stbr_info->filter);
stbr__calculate_sample_range_downsample(n_adjusted, in_pixels_radius, scale_ratio, &out_first_texel, &out_last_texel, &out_center_of_in);
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stbr__calculate_coefficients_downsample(stbr_info, scale_ratio, out_first_texel, out_last_texel, out_center_of_in, stbr__get_contributor(stbr_info, n), stbr__get_coefficient(stbr_info, n, 0));
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}
}
}
static float* stbr__get_decode_buffer(stbr__info* stbr_info)
{
// The 0 index of the decode buffer starts after the margin. This makes
// it okay to use negative indexes on the decode buffer.
return &stbr_info->decode_buffer[stbr__get_filter_texel_margin(stbr_info->filter) * stbr_info->channels];
}
static void stbr__decode_scanline(stbr__info* stbr_info, int n)
{
int x, c;
int channels = stbr_info->channels;
int input_w = stbr_info->input_w;
int input_stride_bytes = stbr_info->input_stride_bytes;
const void* input_data = stbr_info->input_data;
float* decode_buffer = stbr__get_decode_buffer(stbr_info);
stbr_edge edge = stbr_info->edge;
int in_buffer_row_index = stbr__edge_wrap(edge, n, stbr_info->input_h) * input_stride_bytes;
int max_x = input_w + stbr__get_filter_texel_margin(stbr_info->filter);
STBR_UNIMPLEMENTED(stbr_info->type != STBR_TYPE_UINT8);
for (x = -stbr__get_filter_texel_margin(stbr_info->filter); x < max_x; x++)
{
int decode_texel_index = x * channels;
int input_texel_index = in_buffer_row_index + stbr__edge_wrap(edge, x, input_w) * channels;
for (c = 0; c < channels; c++)
decode_buffer[decode_texel_index + c] = ((float)((const unsigned char*)input_data)[input_texel_index + c]) / 255;
}
}
static float* stbr__get_ring_buffer_entry(float* ring_buffer, int index, int ring_buffer_length)
{
return &ring_buffer[index * ring_buffer_length];
}
static float* stbr__add_empty_ring_buffer_entry(stbr__info* stbr_info, int n)
{
int ring_buffer_index;
float* ring_buffer;
if (stbr_info->ring_buffer_begin_index < 0)
{
ring_buffer_index = stbr_info->ring_buffer_begin_index = 0;
stbr_info->ring_buffer_first_scanline = n;
}
else
{
ring_buffer_index = (stbr_info->ring_buffer_begin_index + (stbr_info->ring_buffer_last_scanline - stbr_info->ring_buffer_first_scanline) + 1) % stbr__get_filter_texel_width(stbr_info->filter);
STBR_DEBUG_ASSERT(ring_buffer_index != stbr_info->ring_buffer_begin_index);
}
ring_buffer = stbr__get_ring_buffer_entry(stbr_info->ring_buffer, ring_buffer_index, stbr_info->ring_buffer_length_bytes / sizeof(float));
memset(ring_buffer, 0, stbr_info->ring_buffer_length_bytes);
stbr_info->ring_buffer_last_scanline = n;
return ring_buffer;
}
static void stbr__resample_horizontal_upsample(stbr__info* stbr_info, int n, float* output_buffer)
{
int x, k, c;
int output_w = stbr_info->output_w;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
int channels = stbr_info->channels;
float* decode_buffer = stbr__get_decode_buffer(stbr_info);
stbr__contributors* horizontal_contributors = stbr_info->horizontal_contributors;
float* horizontal_coefficients = stbr_info->horizontal_coefficients;
for (x = 0; x < output_w; x++)
{
int n0 = horizontal_contributors[x].n0;
int n1 = horizontal_contributors[x].n1;
int out_texel_index = x * channels;
int coefficient_group_index = x * kernel_texel_width;
int coefficient_counter = 0;
STBR_DEBUG_ASSERT(n1 >= n0);
STBR_DEBUG_ASSERT(n0 >= -stbr__get_filter_texel_margin(stbr_info->filter));
STBR_DEBUG_ASSERT(n1 >= -stbr__get_filter_texel_margin(stbr_info->filter));
STBR_DEBUG_ASSERT(n0 < stbr_info->input_w + stbr__get_filter_texel_margin(stbr_info->filter));
STBR_DEBUG_ASSERT(n1 < stbr_info->input_w + stbr__get_filter_texel_margin(stbr_info->filter));
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_group_index + (coefficient_counter++);
int in_texel_index = k * channels;
float coefficient = horizontal_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
output_buffer[out_texel_index + c] += decode_buffer[in_texel_index + c] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + c] <= 1.0f);
}
}
}
}
static void stbr__resample_horizontal_downsample(stbr__info* stbr_info, int n, float* output_buffer)
{
int x, k, c;
int input_w = stbr_info->input_w;
int output_w = stbr_info->output_w;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
int channels = stbr_info->channels;
float* decode_buffer = stbr__get_decode_buffer(stbr_info);
stbr__contributors* horizontal_contributors = stbr_info->horizontal_contributors;
float* horizontal_coefficients = stbr_info->horizontal_coefficients;
int filter_texel_margin = stbr__get_filter_texel_margin(stbr_info->filter);
int max_x = input_w + filter_texel_margin * 2;
STBR_DEBUG_ASSERT(!stbr__use_width_upsampling(stbr_info));
for (x = 0; x < max_x; x++)
{
int n0 = horizontal_contributors[x].n0;
int n1 = horizontal_contributors[x].n1;
int in_x = x - filter_texel_margin;
int in_texel_index = in_x * channels;
int max_n = stbr__min(n1, output_w-1);
int coefficient_group = x*kernel_texel_width;
STBR_DEBUG_ASSERT(n1 >= n0);
// Using min and max to avoid writing into invalid texels.
for (k = stbr__max(n0, 0); k <= max_n; k++)
{
int coefficient_index = (k - n0) + coefficient_group;
int out_texel_index = k * channels;
float coefficient = horizontal_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
output_buffer[out_texel_index + c] += decode_buffer[in_texel_index + c] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + c] <= 1.0); // This would indicate that the sum of kernels for this texel doesn't add to 1.
}
}
}
}
static void stbr__decode_and_resample_upsample(stbr__info* stbr_info, int n)
{
// Decode the nth scanline from the source image into the decode buffer.
stbr__decode_scanline(stbr_info, n);
// Now resample it into the ring buffer.
if (stbr__use_width_upsampling(stbr_info))
stbr__resample_horizontal_upsample(stbr_info, n, stbr__add_empty_ring_buffer_entry(stbr_info, n));
else
stbr__resample_horizontal_downsample(stbr_info, n, stbr__add_empty_ring_buffer_entry(stbr_info, n));
// Now it's sitting in the ring buffer ready to be used as source for the vertical sampling.
}
static void stbr__decode_and_resample_downsample(stbr__info* stbr_info, int n)
{
// Decode the nth scanline from the source image into the decode buffer.
stbr__decode_scanline(stbr_info, n);
memset(stbr_info->horizontal_buffer, 0, stbr_info->output_w * stbr_info->channels * sizeof(float));
// Now resample it into the horizontal buffer.
if (stbr__use_width_upsampling(stbr_info))
stbr__resample_horizontal_upsample(stbr_info, n, stbr_info->horizontal_buffer);
else
stbr__resample_horizontal_downsample(stbr_info, n, stbr_info->horizontal_buffer);
// Now it's sitting in the horizontal buffer ready to be distributed into the ring buffers.
}
// Get the specified scan line from the ring buffer.
static float* stbr__get_ring_buffer_scanline(int get_scanline, float* ring_buffer, int begin_index, int first_scanline, int ring_buffer_size, int ring_buffer_length)
{
int ring_buffer_index = (begin_index + (get_scanline - first_scanline)) % ring_buffer_size;
return stbr__get_ring_buffer_entry(ring_buffer, ring_buffer_index, ring_buffer_length);
}
static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int in_first_scanline, int in_last_scanline, float in_center_of_out)
{
int x, k, c;
int output_w = stbr_info->output_w;
stbr__contributors* vertical_contributors = &stbr_info->vertical_contributors;
float* vertical_coefficients = stbr_info->vertical_coefficients;
int channels = stbr_info->channels;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
void* output_data = stbr_info->output_data;
float* encode_buffer = stbr_info->encode_buffer;
float* ring_buffer = stbr_info->ring_buffer;
int ring_buffer_begin_index = stbr_info->ring_buffer_begin_index;
int ring_buffer_first_scanline = stbr_info->ring_buffer_first_scanline;
int ring_buffer_last_scanline = stbr_info->ring_buffer_last_scanline;
int ring_buffer_length = stbr_info->ring_buffer_length_bytes/sizeof(float);
STBR_UNIMPLEMENTED(stbr_info->type != STBR_TYPE_UINT8);
stbr__calculate_coefficients_upsample(stbr_info, in_first_scanline, in_last_scanline, in_center_of_out, vertical_contributors, vertical_coefficients);
int n0 = vertical_contributors->n0;
int n1 = vertical_contributors->n1;
int output_row_index = n * stbr_info->output_stride_bytes;
STBR_DEBUG_ASSERT(stbr__use_height_upsampling(stbr_info));
STBR_DEBUG_ASSERT(n0 >= in_first_scanline);
STBR_DEBUG_ASSERT(n1 <= in_last_scanline);
for (x = 0; x < output_w; x++)
{
int in_texel_index = x * channels;
int out_texel_index = output_row_index + x * channels;
int coefficient_counter = 0;
STBR_DEBUG_ASSERT(n1 >= n0);
memset(encode_buffer, 0, sizeof(float) * channels);
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbr__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_texel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
encode_buffer[c] += ring_buffer_entry[in_texel_index + c] * coefficient;
}
for (c = 0; c < channels; c++)
((unsigned char*)output_data)[out_texel_index + c] = (unsigned char)(encode_buffer[c] * 255);
}
}
static void stbr__resample_vertical_downsample(stbr__info* stbr_info, int n, int in_first_scanline, int in_last_scanline, float in_center_of_out)
{
int x, k, c;
int output_w = stbr_info->output_w;
int output_h = stbr_info->output_h;
stbr__contributors* vertical_contributors = &stbr_info->vertical_contributors;
float* vertical_coefficients = stbr_info->vertical_coefficients;
int channels = stbr_info->channels;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
void* output_data = stbr_info->output_data;
float* horizontal_buffer = stbr_info->horizontal_buffer;
float* ring_buffer = stbr_info->ring_buffer;
int ring_buffer_begin_index = stbr_info->ring_buffer_begin_index;
int ring_buffer_first_scanline = stbr_info->ring_buffer_first_scanline;
int ring_buffer_last_scanline = stbr_info->ring_buffer_last_scanline;
int ring_buffer_length = stbr_info->ring_buffer_length_bytes/sizeof(float);
stbr__calculate_coefficients_downsample(stbr_info, (float)stbr_info->output_h / stbr_info->input_h, in_first_scanline, in_last_scanline, in_center_of_out, vertical_contributors, vertical_coefficients);
int n0 = vertical_contributors->n0;
int n1 = vertical_contributors->n1;
STBR_DEBUG_ASSERT(!stbr__use_height_upsampling(stbr_info));
STBR_DEBUG_ASSERT(n0 >= in_first_scanline);
STBR_DEBUG_ASSERT(n1 <= in_last_scanline);
for (x = 0; x < output_w; x++)
{
int in_texel_index = x * channels;
int max_n = stbr__min(n1, output_h-1);
STBR_DEBUG_ASSERT(n1 >= n0);
// Using min and max to avoid writing into ring buffers that will be thrown out.
for (k = stbr__max(n0, 0); k <= max_n; k++)
{
int coefficient_index = k - n0;
float* ring_buffer_entry = stbr__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_texel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
int index = in_texel_index + c;
ring_buffer_entry[index] += horizontal_buffer[index] * coefficient;
STBR_DEBUG_ASSERT(ring_buffer_entry[index] <= 1.0); // This would indicate that the sum of kernels for this texel doesn't add to 1.
}
}
}
}
static void stbr__buffer_loop_upsample(stbr__info* stbr_info)
{
int y;
float scale_ratio = (float)stbr_info->output_h / stbr_info->input_h;
float out_scanlines_radius = stbr__filter_info_table[stbr_info->filter].support * scale_ratio;
STBR_DEBUG_ASSERT(stbr__use_height_upsampling(stbr_info));
for (y = 0; y < stbr_info->output_h; y++)
{
float in_center_of_out = 0; // Center of the current out scanline in the in scanline space
int in_first_scanline = 0, in_last_scanline = 0;
stbr__calculate_sample_range_upsample(y, out_scanlines_radius, scale_ratio, &in_first_scanline, &in_last_scanline, &in_center_of_out);
STBR_DEBUG_ASSERT(in_last_scanline - in_first_scanline <= stbr__get_filter_texel_width(stbr_info->filter));
STBR_DEBUG_ASSERT(in_first_scanline >= -stbr__get_filter_texel_margin(stbr_info->filter));
STBR_DEBUG_ASSERT(in_last_scanline < stbr_info->input_w + stbr__get_filter_texel_margin(stbr_info->filter));
if (stbr_info->ring_buffer_begin_index >= 0)
{
// Get rid of whatever we don't need anymore.
while (in_first_scanline > stbr_info->ring_buffer_first_scanline)
{
if (stbr_info->ring_buffer_first_scanline == stbr_info->ring_buffer_last_scanline)
{
// We just popped the last scanline off the ring buffer.
// Reset it to the empty state.
stbr_info->ring_buffer_begin_index = -1;
stbr_info->ring_buffer_first_scanline = 0;
stbr_info->ring_buffer_last_scanline = 0;
break;
}
else
{
stbr_info->ring_buffer_first_scanline++;
stbr_info->ring_buffer_begin_index = (stbr_info->ring_buffer_begin_index + 1) % stbr__get_filter_texel_width(stbr_info->filter);
}
}
}
// Load in new ones.
if (stbr_info->ring_buffer_begin_index < 0)
stbr__decode_and_resample_upsample(stbr_info, in_first_scanline);
while (in_last_scanline > stbr_info->ring_buffer_last_scanline)
stbr__decode_and_resample_upsample(stbr_info, stbr_info->ring_buffer_last_scanline + 1);
// Now all buffers should be ready to write a row of vertical sampling.
stbr__resample_vertical_upsample(stbr_info, y, in_first_scanline, in_last_scanline, in_center_of_out);
}
}
static void stbr__empty_ring_buffer(stbr__info* stbr_info, int first_necessary_scanline)
{
int output_stride_bytes = stbr_info->output_stride_bytes;
int channels = stbr_info->channels;
int output_w = stbr_info->output_w;
void* output_data = stbr_info->output_data;
float* ring_buffer = stbr_info->ring_buffer;
int ring_buffer_length = stbr_info->ring_buffer_length_bytes/sizeof(float);
if (stbr_info->ring_buffer_begin_index >= 0)
{
// Get rid of whatever we don't need anymore.
while (first_necessary_scanline > stbr_info->ring_buffer_first_scanline || first_necessary_scanline < 0)
{
int x, c;
int output_row = stbr_info->ring_buffer_first_scanline * output_stride_bytes;
float* ring_buffer_entry = stbr__get_ring_buffer_entry(ring_buffer, stbr_info->ring_buffer_begin_index, ring_buffer_length);
STBR_UNIMPLEMENTED(stbr_info->type != STBR_TYPE_UINT8);
if (stbr_info->ring_buffer_first_scanline >= 0 && stbr_info->ring_buffer_first_scanline < stbr_info->output_h)
{
for (x = 0; x < output_w; x++)
{
int texel_index = x * channels;
int ring_texel_index = texel_index;
int output_texel_index = output_row + texel_index;
for (c = 0; c < channels; c++)
((unsigned char*)output_data)[output_texel_index + c] = (unsigned char)(ring_buffer_entry[ring_texel_index + c] * 255);
}
}
if (stbr_info->ring_buffer_first_scanline == stbr_info->ring_buffer_last_scanline)
{
// We just popped the last scanline off the ring buffer.
// Reset it to the empty state.
stbr_info->ring_buffer_begin_index = -1;
stbr_info->ring_buffer_first_scanline = 0;
stbr_info->ring_buffer_last_scanline = 0;
break;
}
else
{
stbr_info->ring_buffer_first_scanline++;
stbr_info->ring_buffer_begin_index = (stbr_info->ring_buffer_begin_index + 1) % stbr__get_filter_texel_width(stbr_info->filter);
}
}
}
}
static void stbr__buffer_loop_downsample(stbr__info* stbr_info)
{
int y;
float scale_ratio = (float)stbr_info->output_h / stbr_info->input_h;
float in_pixels_radius = stbr__filter_info_table[stbr_info->filter].support / scale_ratio;
STBR_DEBUG_ASSERT(!stbr__use_height_upsampling(stbr_info));
for (y = 0; y < stbr_info->input_h; y++)
{
float out_center_of_in; // Center of the current out scanline in the in scanline space
int out_first_scanline, out_last_scanline;
stbr__calculate_sample_range_downsample(y, in_pixels_radius, scale_ratio, &out_first_scanline, &out_last_scanline, &out_center_of_in);
STBR_DEBUG_ASSERT(out_last_scanline - out_first_scanline <= stbr__get_filter_texel_width(stbr_info->filter));
STBR_DEBUG_ASSERT(out_first_scanline >= -stbr__get_filter_texel_margin(stbr_info->filter));
STBR_DEBUG_ASSERT(out_last_scanline < stbr_info->input_w + stbr__get_filter_texel_margin(stbr_info->filter));
stbr__empty_ring_buffer(stbr_info, out_first_scanline);
stbr__decode_and_resample_downsample(stbr_info, y);
// Load in new ones.
if (stbr_info->ring_buffer_begin_index < 0)
stbr__add_empty_ring_buffer_entry(stbr_info, out_first_scanline);
while (out_last_scanline > stbr_info->ring_buffer_last_scanline)
stbr__add_empty_ring_buffer_entry(stbr_info, stbr_info->ring_buffer_last_scanline + 1);
// Now the horizontal buffer is ready to write to all ring buffer rows.
stbr__resample_vertical_downsample(stbr_info, y, out_first_scanline, out_last_scanline, out_center_of_in);
}
stbr__empty_ring_buffer(stbr_info, -1);
}
STBRDEF int stbr_resize_arbitrary(const void* input_data, int input_w, int input_h, int input_stride_in_bytes,
void* output_data, int output_w, int output_h, int output_stride_in_bytes,
int channels, stbr_type type, stbr_filter filter, stbr_edge edge,
void* tempmem, stbr_size_t tempmem_size_in_bytes)
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{
int width_stride_input = input_stride_in_bytes ? input_stride_in_bytes : channels * input_w;
int width_stride_output = output_stride_in_bytes ? output_stride_in_bytes : channels * output_w;
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#ifdef STBR_DEBUG_OVERWRITE_TEST
#define OVERWRITE_ARRAY_SIZE 64
unsigned char overwrite_output_pre[OVERWRITE_ARRAY_SIZE];
unsigned char overwrite_tempmem_pre[OVERWRITE_ARRAY_SIZE];
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stbr_size_t begin_forbidden = width_stride_output * (output_h - 1) + output_w * channels;
memcpy(overwrite_output_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE);
memcpy(overwrite_tempmem_pre, &((unsigned char*)tempmem)[tempmem_size_in_bytes], OVERWRITE_ARRAY_SIZE);
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#endif
STBR_UNIMPLEMENTED(type != STBR_TYPE_UINT8);
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STBR_ASSERT(filter != 0);
STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
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if (!tempmem)
return 0;
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if (tempmem_size_in_bytes < stbr_calculate_memory(input_w, input_h, input_stride_in_bytes, output_w, output_h, output_stride_in_bytes, channels, STBR_FILTER_NEAREST))
return 0;
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memset(tempmem, 0, tempmem_size_in_bytes);
stbr__info* stbr_info = (stbr__info*)tempmem;
stbr_info->input_data = input_data;
stbr_info->input_w = input_w;
stbr_info->input_h = input_h;
stbr_info->input_stride_bytes = width_stride_input;
stbr_info->output_data = output_data;
stbr_info->output_w = output_w;
stbr_info->output_h = output_h;
stbr_info->output_stride_bytes = width_stride_output;
stbr_info->channels = channels;
stbr_info->type = type;
stbr_info->filter = filter;
stbr_info->edge = edge;
stbr_info->ring_buffer_length_bytes = output_w * channels * sizeof(float);
stbr_info->decode_buffer_texels = input_w + stbr__get_filter_texel_margin(filter) * 2;
#define STBR__NEXT_MEMPTR(current, old, newtype) (newtype*)(((unsigned char*)current) + old)
stbr_info->horizontal_contributors = STBR__NEXT_MEMPTR(stbr_info, sizeof(stbr__info), stbr__contributors);
stbr_info->horizontal_coefficients = STBR__NEXT_MEMPTR(stbr_info->horizontal_contributors, stbr__get_horizontal_contributors(filter, input_w, output_w) * sizeof(stbr__contributors), float);
stbr_info->vertical_coefficients = STBR__NEXT_MEMPTR(stbr_info->horizontal_coefficients, stbr__get_total_coefficients(filter, input_w, output_w) * sizeof(float), float);
stbr_info->decode_buffer = STBR__NEXT_MEMPTR(stbr_info->vertical_coefficients, stbr__get_filter_texel_width(filter) * sizeof(float), float);
if (stbr__use_height_upsampling(stbr_info))
{
stbr_info->horizontal_buffer = NULL;
stbr_info->ring_buffer = STBR__NEXT_MEMPTR(stbr_info->decode_buffer, stbr_info->decode_buffer_texels * channels * sizeof(float), float);
stbr_info->encode_buffer = STBR__NEXT_MEMPTR(stbr_info->ring_buffer, stbr_info->ring_buffer_length_bytes * stbr__get_filter_texel_width(filter), float);
STBR_DEBUG_ASSERT((size_t)STBR__NEXT_MEMPTR(stbr_info->encode_buffer, stbr_info->channels * sizeof(float), unsigned char) == (size_t)tempmem + tempmem_size_in_bytes);
}
else
{
stbr_info->horizontal_buffer = STBR__NEXT_MEMPTR(stbr_info->decode_buffer, stbr_info->decode_buffer_texels * channels * sizeof(float), float);
stbr_info->ring_buffer = STBR__NEXT_MEMPTR(stbr_info->horizontal_buffer, output_w * channels * sizeof(float), float);
stbr_info->encode_buffer = NULL;
STBR_DEBUG_ASSERT((size_t)STBR__NEXT_MEMPTR(stbr_info->ring_buffer, stbr_info->ring_buffer_length_bytes * stbr__get_filter_texel_width(filter), unsigned char) == (size_t)tempmem + tempmem_size_in_bytes);
}
#undef STBR__NEXT_MEMPTR
// This signals that the ring buffer is empty
stbr_info->ring_buffer_begin_index = -1;
stbr__calculate_horizontal_filters(stbr_info);
if (stbr__use_height_upsampling(stbr_info))
stbr__buffer_loop_upsample(stbr_info);
else
stbr__buffer_loop_downsample(stbr_info);
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#ifdef STBR_DEBUG_OVERWRITE_TEST
STBR_DEBUG_ASSERT(memcmp(overwrite_output_pre, &((unsigned char*)output_data)[begin_forbidden], OVERWRITE_ARRAY_SIZE) == 0);
STBR_DEBUG_ASSERT(memcmp(overwrite_tempmem_pre, &((unsigned char*)tempmem)[tempmem_size_in_bytes], OVERWRITE_ARRAY_SIZE) == 0);
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#endif
return 1;
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}
STBRDEF stbr_size_t stbr_calculate_memory(int input_w, int input_h, int input_stride_in_bytes,
int output_w, int output_h, int output_stride_in_bytes,
int channels, stbr_filter filter)
{
STBR_ASSERT(filter != 0);
STBR_ASSERT(filter < STBR_ARRAY_SIZE(stbr__filter_info_table));
int texel_margin = stbr__get_filter_texel_margin(filter);
int info_size = sizeof(stbr__info);
int contributors_size = stbr__get_horizontal_contributors(filter, input_w, output_w) * sizeof(stbr__contributors);
int horizontal_coefficients_size = stbr__get_total_coefficients(filter, input_w, output_w) * sizeof(float);
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int vertical_coefficients_size = stbr__get_filter_texel_width(filter) * sizeof(float);
int decode_buffer_size = (input_w + texel_margin*2) * channels * sizeof(float);
int horizontal_buffer_size = output_w * channels * sizeof(float);
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int ring_buffer_size = output_w * channels * sizeof(float) * stbr__get_filter_texel_width(filter);
int encode_buffer_size = channels * sizeof(float);
if (stbr__use_height_upsampling_noinfo(output_h, input_h))
// The horizontal buffer is for when we're downsampling the height and we
// can't output the result of sampling the decode buffer directly into the
// ring buffers.
horizontal_buffer_size = 0;
else
// The encode buffer is to retain precision in the height upsampling method
// and isn't used when height downsampling.
encode_buffer_size = 0;
return info_size + contributors_size + horizontal_coefficients_size + vertical_coefficients_size + decode_buffer_size + horizontal_buffer_size + ring_buffer_size + encode_buffer_size;
}
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#endif // STB_RESAMPLE_IMPLEMENTATION
/*
revision history:
*/