在前面的文章，我提到过VSCO Cam 的胶片滤镜算法实现是3d lut。
那么3d lut 到底是个什么东西呢？
或者说它是用来做什么的？
长话短说，3d lut(全称 : 3D Lookup table )它是通过建立一个颜色映射表，对图像的色调进行重调的算法。
有用于摄像机的效果美化润色，例如一些所谓的数码相机之类的。
也有用于影视后期调色，渲染影视作品的颜色基调等等。
简单的说，你想要把图片上的一些颜色通过你自己的预设给替换掉。
例如红色换成白色，白色换成绿色。
当然这在现实中操作起来非常复杂。
因为 RGB888(8+8+8=24位色):
(2^8)*(2^8)*(2^8)=
256*256*256=16777216
有16M 种颜色，如果采用手工操作的方式一个一个颜色地换，那人还活不活了。
所以就有通过建立映射表进行插值达到逼近这种效果的算法。
它就是3d lut，当然也有2d lut，1d lut。
精度不一，效果不一。
例如：
调节亮度 可以认为是1d lut.
调节对比度 可以认为是 2d lut.
而调节整体的色调最佳肯定是3d lut.
当然2d lut 也是可以做到，但是精度就没有那么高了。
我之前也提到过，市面有不少app是采用2d LUT,毕竟精度不需要那么高。
2d够用了。
但是在摄影界，影视后期这一行当里，3d lut是标配。
相关资料可以参阅:
在VSCO Cam APP中滤镜效果每一档都是一个17*17*17的3d lut预设。
先上个图，大家感受一下。
只是一个例子，效果是看做预设的功底的。
那么3d lut 的实现具体是什么算法呢？
当然据我所知，Trilinear_interpolation 是用得最广泛的一种。
之前做APP滤镜的时候，调研过不少资料。
但是当时发现一些开源项目的实现是有问题的，插值算错坐标之类的。
有一次心血来潮，去翻了翻FFmpeg的代码，居然发现了它也有实现3d lut算法。
嗯，站在巨人的肩膀上。
抽了点时间对FFmpeg中的3d lut 进行了整理。
提取出它的算法，并编写示例。
当然未经过严格验证，应该存在一些小Bugs。
完整示例代码献上：
/* * Copyright (c) 2013 Clément Bœsch * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * 3D Lookup table filter */ #include "browse.h" #define USE_SHELL_OPEN #define STB_IMAGE_STATIC #define STB_IMAGE_IMPLEMENTATION #include "stb_image.h" /* ref:https://github.com/nothings/stb/blob/master/stb_image.h */ #define TJE_IMPLEMENTATION #include "tiny_jpeg.h" /* ref:https://github.com/serge-rgb/TinyJPEG/blob/master/tiny_jpeg.h */ #include <math.h> #include <stdbool.h> #include <stdio.h> #include "timing.h" #include <stdint.h> #include <assert.h> #ifndef _MAX_DRIVE #define _MAX_DRIVE 3 #endif #ifndef _MAX_FNAME #define _MAX_FNAME 256 #endif #ifndef _MAX_EXT #define _MAX_EXT 256 #endif #ifndef _MAX_DIR #define _MAX_DIR 256 #endif #ifdef _MSC_VER #endif #ifndef MIN #define MIN(a, b) ( (a) > (b) ? (b) : (a) ) #endif #ifndef _NEAR #define _NEAR(x) ( (int) ( (x) + .5) ) #endif #ifndef PREV #define PREV(x) ( (int) (x) ) #endif #ifndef NEXT #define NEXT(x) (MIN( (int) (x) + 1, lut3d->lutsize - 1 ) ) #endif #ifndef R #define R 0 #endif #ifndef G #define G 1 #endif #ifndef B #define B 2 #endif #ifndef A #define A 3 #endif #ifndef MAX_LEVEL #define MAX_LEVEL 64 #endif enum interp_mode { INTERPOLATE_NEAREST, INTERPOLATE_TRILINEAR, INTERPOLATE_TETRAHEDRAL, NB_INTERP_MODE }; struct rgbvec { float r, g, b; }; /* 3D LUT don't often go up to level 32 */ typedef struct LUT3DContext { uint8_t rgba_map[4]; int step; struct rgbvec lut[MAX_LEVEL][MAX_LEVEL][MAX_LEVEL]; int lutsize; } LUT3DContext; #ifdef _MSC_VER int strcasecmp(const char *s1, char *s2) { while (toupper((unsigned char)*s1) == toupper((unsigned char)*s2++)) if (*s1++ == 0x00) return (0); return (toupper((unsigned char)*s1) - toupper((unsigned char) *--s2)); } #endif static inline float lerpf(float v0, float v1, float f) { return (v0 + (v1 - v0) * f); } static inline struct rgbvec lerp(const struct rgbvec *v0, const struct rgbvec *v1, float f) { struct rgbvec v = { lerpf(v0->r, v1->r, f), lerpf(v0->g, v1->g, f), lerpf(v0->b, v1->b, f) }; return (v); } /** * Get the nearest defined point */ static inline struct rgbvec interp_nearest(const LUT3DContext *lut3d, const struct rgbvec *s) { return (lut3d->lut[_NEAR(s->r)][_NEAR(s->g)][_NEAR(s->b)]); } /** * Interpolate using the 8 vertices of a cube * @see https://en.wikipedia.org/wiki/Trilinear_interpolation */ static inline struct rgbvec interp_trilinear(const LUT3DContext *lut3d, const struct rgbvec *s) { const int prev[] = {PREV(s->r), PREV(s->g), PREV(s->b)}; const int next[] = {NEXT(s->r), NEXT(s->g), NEXT(s->b)}; const struct rgbvec d = {s->r - prev[0], s->g - prev[1], s->b - prev[2]}; const struct rgbvec c000 = lut3d->lut[prev[0]][prev[1]][prev[2]]; const struct rgbvec c001 = lut3d->lut[prev[0]][prev[1]][next[2]]; const struct rgbvec c010 = lut3d->lut[prev[0]][next[1]][prev[2]]; const struct rgbvec c011 = lut3d->lut[prev[0]][next[1]][next[2]]; const struct rgbvec c100 = lut3d->lut[next[0]][prev[1]][prev[2]]; const struct rgbvec c101 = lut3d->lut[next[0]][prev[1]][next[2]]; const struct rgbvec c110 = lut3d->lut[next[0]][next[1]][prev[2]]; const struct rgbvec c111 = lut3d->lut[next[0]][next[1]][next[2]]; const struct rgbvec c00 = lerp(&c000, &c100, d.r); const struct rgbvec c10 = lerp(&c010, &c110, d.r); const struct rgbvec c01 = lerp(&c001, &c101, d.r); const struct rgbvec c11 = lerp(&c011, &c111, d.r); const struct rgbvec c0 = lerp(&c00, &c10, d.g); const struct rgbvec c1 = lerp(&c01, &c11, d.g); const struct rgbvec c = lerp(&c0, &c1, d.b); return (c); } /** * Tetrahedral interpolation. Based on code found in Truelight Software Library paper. * @see http://www.filmlight.ltd.uk/pdf/whitepapers/FL-TL-TN-0057-SoftwareLib.pdf */ static inline struct rgbvec interp_tetrahedral(const LUT3DContext *lut3d, const struct rgbvec *s) { const int prev[] = {PREV(s->r), PREV(s->g), PREV(s->b)}; const int next[] = {NEXT(s->r), NEXT(s->g), NEXT(s->b)}; const struct rgbvec d = {s->r - prev[0], s->g - prev[1], s->b - prev[2]}; const struct rgbvec c000 = lut3d->lut[prev[0]][prev[1]][prev[2]]; const struct rgbvec c111 = lut3d->lut[next[0]][next[1]][next[2]]; struct rgbvec c; if (d.r > d.g) { if (d.g > d.b) { const struct rgbvec c100 = lut3d->lut[next[0]][prev[1]][prev[2]]; const struct rgbvec c110 = lut3d->lut[next[0]][next[1]][prev[2]]; c.r = (1 - d.r) * c000.r + (d.r - d.g) * c100.r + (d.g - d.b) * c110.r + (d.b) * c111.r; c.g = (1 - d.r) * c000.g + (d.r - d.g) * c100.g + (d.g - d.b) * c110.g + (d.b) * c111.g; c.b = (1 - d.r) * c000.b + (d.r - d.g) * c100.b + (d.g - d.b) * c110.b + (d.b) * c111.b; } else if (d.r > d.b) { const struct rgbvec c100 = lut3d->lut[next[0]][prev[1]][prev[2]]; const struct rgbvec c101 = lut3d->lut[next[0]][prev[1]][next[2]]; c.r = (1 - d.r) * c000.r + (d.r - d.b) * c100.r + (d.b - d.g) * c101.r + (d.g) * c111.r; c.g = (1 - d.r) * c000.g + (d.r - d.b) * c100.g + (d.b - d.g) * c101.g + (d.g) * c111.g; c.b = (1 - d.r) * c000.b + (d.r - d.b) * c100.b + (d.b - d.g) * c101.b + (d.g) * c111.b; } else { const struct rgbvec c001 = lut3d->lut[prev[0]][prev[1]][next[2]]; const struct rgbvec c101 = lut3d->lut[next[0]][prev[1]][next[2]]; c.r = (1 - d.b) * c000.r + (d.b - d.r) * c001.r + (d.r - d.g) * c101.r + (d.g) * c111.r; c.g = (1 - d.b) * c000.g + (d.b - d.r) * c001.g + (d.r - d.g) * c101.g + (d.g) * c111.g; c.b = (1 - d.b) * c000.b + (d.b - d.r) * c001.b + (d.r - d.g) * c101.b + (d.g) * c111.b; } } else { if (d.b > d.g) { const struct rgbvec c001 = lut3d->lut[prev[0]][prev[1]][next[2]]; const struct rgbvec c011 = lut3d->lut[prev[0]][next[1]][next[2]]; c.r = (1 - d.b) * c000.r + (d.b - d.g) * c001.r + (d.g - d.r) * c011.r + (d.r) * c111.r; c.g = (1 - d.b) * c000.g + (d.b - d.g) * c001.g + (d.g - d.r) * c011.g + (d.r) * c111.g; c.b = (1 - d.b) * c000.b + (d.b - d.g) * c001.b + (d.g - d.r) * c011.b + (d.r) * c111.b; } else if (d.b > d.r) { const struct rgbvec c010 = lut3d->lut[prev[0]][next[1]][prev[2]]; const struct rgbvec c011 = lut3d->lut[prev[0]][next[1]][next[2]]; c.r = (1 - d.g) * c000.r + (d.g - d.b) * c010.r + (d.b - d.r) * c011.r + (d.r) * c111.r; c.g = (1 - d.g) * c000.g + (d.g - d.b) * c010.g + (d.b - d.r) * c011.g + (d.r) * c111.g; c.b = (1 - d.g) * c000.b + (d.g - d.b) * c010.b + (d.b - d.r) * c011.b + (d.r) * c111.b; } else { const struct rgbvec c010 = lut3d->lut[prev[0]][next[1]][prev[2]]; const struct rgbvec c110 = lut3d->lut[next[0]][next[1]][prev[2]]; c.r = (1 - d.g) * c000.r + (d.g - d.r) * c010.r + (d.r - d.b) * c110.r + (d.b) * c111.r; c.g = (1 - d.g) * c000.g + (d.g - d.r) * c010.g + (d.r - d.b) * c110.g + (d.b) * c111.g; c.b = (1 - d.g) * c000.b + (d.g - d.r) * c010.b + (d.r - d.b) * c110.b + (d.b) * c111.b; } } return (c); } /** * Locale-independent conversion of ASCII isspace. */ int _isspace(int c) { return (c == ' ' || c == 'f' || c == ' ' || c == ' ' || c == ' ' || c == 'v'); } /** * Clip a signed integer value into the 0-65535 range. * @param a value to clip * @return clipped value */ static uint16_t clip_uint16(int a) { if (a & (~0xFFFF)) return ((~a) >> 31); else return (a); } /** * Clip a signed integer value into the 0-255 range. * @param a value to clip * @return clipped value */ static uint8_t clip_uint8(int a) { if (a & (~0xFF)) return ((~a) >> 31); else return (a); } static unsigned clip_uintp2(int a, int p) { if (a & ~((1 << p) - 1)) return (-a >> 31 & ((1 << p) - 1)); else return (a); } #define DEFINE_INTERP_FUNC_PLANAR(name, nbits, depth) static int interp_ ## nbits ## _ ## name ## _p ## depth( const LUT3DContext * lut3d, uint8_t * indata_g, uint8_t * indata_b, uint8_t * indata_r, uint8_t * indata_a, uint8_t * outdata_g, uint8_t * outdata_b, uint8_t * outdata_r, uint8_t * outdata_a, int width, int height, int linesize ) { int x, y; int direct = (outdata_g == indata_g); uint8_t *grow = outdata_g ; uint8_t *brow = outdata_b ; uint8_t *rrow = outdata_r ; uint8_t *arow = outdata_a ; const uint8_t *srcgrow = indata_g ; const uint8_t *srcbrow = indata_b ; const uint8_t *srcrrow = indata_r ; const uint8_t *srcarow = indata_a ; const float scale = (1.f / ( (1 << (depth) ) - 1) ) * (lut3d->lutsize - 1); for ( y = 0; y < height; y++ ) { uint ## nbits ## _t * dstg = (uint ## nbits ## _t *)grow; uint ## nbits ## _t * dstb = (uint ## nbits ## _t *)brow; uint ## nbits ## _t * dstr = (uint ## nbits ## _t *)rrow; uint ## nbits ## _t * dsta = (uint ## nbits ## _t *)arow; const uint ## nbits ## _t *srcg = (const uint ## nbits ## _t *)srcgrow; const uint ## nbits ## _t *srcb = (const uint ## nbits ## _t *)srcbrow; const uint ## nbits ## _t *srcr = (const uint ## nbits ## _t *)srcrrow; const uint ## nbits ## _t *srca = (const uint ## nbits ## _t *)srcarow; for ( x = 0; x < width; x++ ) { const struct rgbvec scaled_rgb = { srcr[x] * scale, srcg[x] * scale, srcb[x] * scale }; struct rgbvec vec = interp_ ## name( lut3d, &scaled_rgb ); dstr[x] = clip_uintp2( vec.r * (float) ( (1 << (depth) ) - 1), depth ); dstg[x] = clip_uintp2( vec.g * (float) ( (1 << (depth) ) - 1), depth ); dstb[x] = clip_uintp2( vec.b * (float) ( (1 << (depth) ) - 1), depth ); if ( !direct && linesize ) dsta[x] = srca[x]; } grow += linesize; brow += linesize; rrow += linesize; arow += linesize; srcgrow += linesize; srcbrow += linesize; srcrrow += linesize; srcarow += linesize; } return 0; } DEFINE_INTERP_FUNC_PLANAR(nearest, 8, 8) DEFINE_INTERP_FUNC_PLANAR(trilinear, 8, 8) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 8, 8) DEFINE_INTERP_FUNC_PLANAR(nearest, 16, 9) DEFINE_INTERP_FUNC_PLANAR(trilinear, 16, 9) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 16, 9) DEFINE_INTERP_FUNC_PLANAR(nearest, 16, 10) DEFINE_INTERP_FUNC_PLANAR(trilinear, 16, 10) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 16, 10) DEFINE_INTERP_FUNC_PLANAR(nearest, 16, 12) DEFINE_INTERP_FUNC_PLANAR(trilinear, 16, 12) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 16, 12) DEFINE_INTERP_FUNC_PLANAR(nearest, 16, 14) DEFINE_INTERP_FUNC_PLANAR(trilinear, 16, 14) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 16, 14) DEFINE_INTERP_FUNC_PLANAR(nearest, 16, 16) DEFINE_INTERP_FUNC_PLANAR(trilinear, 16, 16) DEFINE_INTERP_FUNC_PLANAR(tetrahedral, 16, 16) #define DEFINE_INTERP_FUNC(name, nbits) static int interp_ ## nbits ## _ ## name( LUT3DContext * lut3d, const uint8_t * indata, uint8_t * outdata, int width, int height, int linesize ) { int x, y; const int direct = outdata == indata; const int step = lut3d->step; const uint8_t r = lut3d->rgba_map[R]; const uint8_t g = lut3d->rgba_map[G]; const uint8_t b = lut3d->rgba_map[B]; const uint8_t a = lut3d->rgba_map[A]; uint8_t *dstrow = outdata; const uint8_t *srcrow = indata; const float scale = (1.f / ( (1 << nbits) - 1) ) * (lut3d->lutsize - 1); for ( y = 0; y < height; y++ ) { uint ## nbits ## _t * dst = (uint ## nbits ## _t *)dstrow; const uint ## nbits ## _t *src = (const uint ## nbits ## _t *)srcrow; for ( x = 0; x < width * step; x += step ) { const struct rgbvec scaled_rgb = { src[x + r] * scale, src[x + g] * scale, src[x + b] * scale }; struct rgbvec vec = interp_ ## name( lut3d, &scaled_rgb ); dst[x + r] = clip_uint ## nbits( vec.r * (float) ( (1 << nbits) - 1) ); dst[x + g] = clip_uint ## nbits( vec.g * (float) ( (1 << nbits) - 1) ); dst[x + b] = clip_uint ## nbits( vec.b * (float) ( (1 << nbits) - 1) ); if ( !direct && step == 4 ) dst[x + a] = src[x + a]; } dstrow += linesize; srcrow += linesize; } return 0; } DEFINE_INTERP_FUNC(nearest, 8) DEFINE_INTERP_FUNC(trilinear, 8) DEFINE_INTERP_FUNC(tetrahedral, 8) DEFINE_INTERP_FUNC(nearest, 16) DEFINE_INTERP_FUNC(trilinear, 16) DEFINE_INTERP_FUNC(tetrahedral, 16) static int skip_line(const char *p) { while (*p && _isspace(*p)) p++; return (!*p || *p == '#'); } #ifndef NEXT_LINE #define NEXT_LINE(loop_cond) do { if ( !fgets( line, sizeof(line), f ) ) { printf( "Unexpected EOF " ); fclose( f ); if ( lut3d ) free( lut3d ); return NULL; } } while ( loop_cond ) #endif #ifndef MAX_LINE_SIZE #define MAX_LINE_SIZE 512 #endif /* Basically r g and b float values on each line, with a facultative 3DLUTSIZE * directive; seems to be generated by Davinci */ LUT3DContext *parse_dat(char *filename) { FILE *f = fopen(filename, "r"); if (f == NULL) return NULL; LUT3DContext *lut3d = NULL; char line[MAX_LINE_SIZE]; int i, j, k, size; int lutsize = size = 33; NEXT_LINE(skip_line(line)); if (!strncmp(line, "3DLUTSIZE ", 10)) { size = strtol(line + 10, NULL, 0); if (size < 2 || size > MAX_LEVEL) { printf("Too large or invalid 3D LUT size "); fclose(f); return (NULL); } lutsize = size; NEXT_LINE(skip_line(line)); } if (size != 0 && lut3d == NULL) { lut3d = (LUT3DContext *) calloc(1, sizeof(LUT3DContext)); } lut3d->lutsize = lutsize; for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { for (i = 0; i < size; i++) { struct rgbvec *vec = &lut3d->lut[k][j][i]; if (k != 0 || j != 0 || i != 0) NEXT_LINE(skip_line(line)); if (sscanf(line, "%f %f %f", &vec->r, &vec->g, &vec->b) != 3) { fclose(f); free(lut3d); return (NULL); } } } } fclose(f); return (lut3d); } LUT3DContext *parse_cube(char *filename) { FILE *f = fopen(filename, "r"); if (f == NULL) return NULL; char line[MAX_LINE_SIZE]; float min[3] = {0.0, 0.0, 0.0}; float max[3] = {1.0, 1.0, 1.0}; int lutsize = 0; LUT3DContext *lut3d = NULL; while (fgets(line, sizeof(line), f)) { if (!strncmp(line, "LUT_3D_SIZE ", 12)) { int i, j, k; const int size = strtol(line + 12, NULL, 0); if (size < 2 || size > MAX_LEVEL) { printf("Too large or invalid 3D LUT size "); fclose(f); return (NULL); } lutsize = size; if (size != 0 && lut3d == NULL) { lut3d = (LUT3DContext *) calloc(1, sizeof(LUT3DContext)); } lut3d->lutsize = lutsize; for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { for (i = 0; i < size; i++) { struct rgbvec *vec = &lut3d->lut[i][j][k]; do { try_again: NEXT_LINE(0); if (!strncmp(line, "DOMAIN_", 7)) { float *vals = NULL; if (!strncmp(line + 7, "MIN ", 4)) vals = min; else if (!strncmp(line + 7, "MAX ", 4)) vals = max; if (!vals) { fclose(f); free(lut3d); return (NULL); } sscanf(line + 11, "%f %f %f", vals, vals + 1, vals + 2); //printf("min: %f %f %f | max: %f %f %f ", min[0], min[1], min[2], max[0], max[1], max[2]); goto try_again; } } while (skip_line(line)); if (sscanf(line, "%f %f %f", &vec->r, &vec->g, &vec->b) != 3) { fclose(f); free(lut3d); return (NULL); } vec->r *= max[0] - min[0]; vec->g *= max[1] - min[1]; vec->b *= max[2] - min[2]; } } } break; } } fclose(f); return (lut3d); } /* Assume 17x17x17 LUT with a 16-bit depth */ LUT3DContext *parse_3dl(char *filename) { FILE *f = fopen(filename, "r"); if (f == NULL) return NULL; char line[MAX_LINE_SIZE]; int i, j, k; const int size = 17; const float scale = 16 * 16 * 16; int lutsize = size; LUT3DContext *lut3d = (LUT3DContext *) calloc(1, sizeof(LUT3DContext)); lut3d->lutsize = lutsize; NEXT_LINE(skip_line(line)); for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { for (i = 0; i < size; i++) { int r, g, b; struct rgbvec *vec = &lut3d->lut[k][j][i]; NEXT_LINE(skip_line(line)); if (sscanf(line, "%d %d %d", &r, &g, &b) != 3) { fclose(f); free(lut3d); return (NULL); } vec->r = r / scale; vec->g = g / scale; vec->b = b / scale; } } } fclose(f); return (lut3d); } /* Pandora format */ LUT3DContext *parse_m3d(char *filename) { FILE *f = fopen(filename, "r"); if (f == NULL) return NULL; float scale; int i, j, k, size, in = -1, out = -1; char line[MAX_LINE_SIZE]; uint8_t rgb_map[3] = {0, 1, 2}; while (fgets(line, sizeof(line), f)) { if (!strncmp(line, "in", 2)) in = strtol(line + 2, NULL, 0); else if (!strncmp(line, "out", 3)) out = strtol(line + 3, NULL, 0); else if (!strncmp(line, "values", 6)) { const char *p = line + 6; #define SET_COLOR(id) do { while ( _isspace( *p ) ) p++; switch ( *p ) { case 'r': rgb_map[id] = 0; break; case 'g': rgb_map[id] = 1; break; case 'b': rgb_map[id] = 2; break; } while ( *p && !_isspace( *p ) ) p++; } while ( 0 ) SET_COLOR(0); SET_COLOR(1); SET_COLOR(2); break; } } if (in == -1 || out == -1) { printf("in and out must be defined "); fclose(f); return (NULL); } if (in < 2 || out < 2 || in > MAX_LEVEL * MAX_LEVEL * MAX_LEVEL || out > MAX_LEVEL * MAX_LEVEL * MAX_LEVEL) { printf("invalid in (%d) or out (%d) ", in, out); fclose(f); return (NULL); } for (size = 1; size * size * size < in; size++); {} int lutsize = size; scale = 1.f / (out - 1); LUT3DContext *lut3d = NULL; if (size != 0) { lut3d = (LUT3DContext *) calloc(1, sizeof(LUT3DContext)); } lut3d->lutsize = lutsize; for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { for (i = 0; i < size; i++) { struct rgbvec *vec = &lut3d->lut[k][j][i]; float val[3]; NEXT_LINE(0); if (sscanf(line, "%f %f %f", val, val + 1, val + 2) != 3) { fclose(f); free(lut3d); return (NULL); } vec->r = val[rgb_map[0]] * scale; vec->g = val[rgb_map[1]] * scale; vec->b = val[rgb_map[2]] * scale; } } } fclose(f); return (lut3d); } LUT3DContext *lut3d_load(char *filename) { int ret = 0; const char *ext; if (!filename) { return (0); } LUT3DContext *lut3d = NULL; ext = strrchr(filename, '.'); if (!ext) { printf("Unable to guess the format from the extension "); goto end; } ext++; if (!strcasecmp(ext, "dat")) { lut3d = parse_dat(filename); } else if (!strcasecmp(ext, "3dl")) { lut3d = parse_3dl(filename); } else if (!strcasecmp(ext, "cube")) { lut3d = parse_cube(filename); } else if (!strcasecmp(ext, "m3d")) { lut3d = parse_m3d(filename); } else { printf("Unrecognized '.%s' file type ", ext); ret = -1; } if (!ret && !lut3d->lutsize) { printf("3D LUT is empty "); } end: return (lut3d); } typedef int (action_planar_func)(const LUT3DContext *lut3d, uint8_t *indata_g, uint8_t *indata_b, uint8_t *indata_r, uint8_t *indata_a, uint8_t *outdata_g, uint8_t *outdata_b, uint8_t *outdata_r, uint8_t *outdata_a, int width, int height, int linesize); static int apply_planar_lut(char *filename, uint8_t *indata_g, uint8_t *indata_b, uint8_t *indata_r, uint8_t *indata_a, uint8_t *outdata_g, uint8_t *outdata_b, uint8_t *outdata_r, uint8_t *outdata_a, int width, int height, int linesize, int depth, int interpolation ) { action_planar_func *interp_func = 0; LUT3DContext *lut3d = lut3d_load(filename); if (lut3d == NULL) return (-1); lut3d->step = depth; int planar = 1; #define SET_PLANAR_FUNC(name) do { if ( planar ) { switch ( depth ) { case 8: interp_func = interp_8_ ## name ## _p8; break; case 9: interp_func = interp_16_ ## name ## _p9; break; case 10: interp_func = interp_16_ ## name ## _p10; break; case 12: interp_func = interp_16_ ## name ## _p12; break; case 14: interp_func = interp_16_ ## name ## _p14; break; case 16: interp_func = interp_16_ ## name ## _p16; break; } } } while ( 0 ) switch (interpolation) { case INTERPOLATE_NEAREST: SET_PLANAR_FUNC(nearest); break; case INTERPOLATE_TRILINEAR: SET_PLANAR_FUNC(trilinear); break; case INTERPOLATE_TETRAHEDRAL: SET_PLANAR_FUNC(tetrahedral); break; default: assert(0); } interp_func(lut3d, indata_g, indata_b, indata_r, indata_a, outdata_g, outdata_b, outdata_r, outdata_a, width, height, linesize); return (0); } typedef int (action_func)(LUT3DContext *lut3d, const uint8_t *indata, uint8_t *outdata, int width, int height, int linesize); static int apply_lut(char *filename, const uint8_t *indata, uint8_t *outdata, int width, int height, int linesize, int depth, int interpolation, int is16bit) { action_func *interp_func = 0; LUT3DContext *lut3d = lut3d_load(filename);
if (lut3d == NULL) return (-1);
lut3d->rgba_map[0] = 0;
lut3d->rgba_map[1] = 1;
lut3d->rgba_map[2] = 2;
lut3d->rgba_map[3] = 3; lut3d->step = depth; #define SET_FUNC(name) do { if ( is16bit ) { interp_func = interp_16_ ## name; } else { interp_func = interp_8_ ## name; } } while ( 0 ) switch (interpolation) { case INTERPOLATE_NEAREST: SET_FUNC(nearest); break; case INTERPOLATE_TRILINEAR: SET_FUNC(trilinear); break; case INTERPOLATE_TETRAHEDRAL: SET_FUNC(tetrahedral); break; default: assert(0); } interp_func(lut3d, indata, outdata, width, height, linesize); free(lut3d); return (0); } char saveFile[1024]; unsigned char *loadImage(const char *filename, int *Width, int *Height, int *Channels) { return (stbi_load(filename, Width, Height, Channels, 0)); } void saveImage(const char *filename, int Width, int Height, int Channels, unsigned char *Output) { memcpy(saveFile + strlen(saveFile), filename, strlen(filename)); *(saveFile + strlen(saveFile) + 1) = 0; if (!tje_encode_to_file(saveFile, Width, Height, Channels, true, Output)) { fprintf(stderr, "save JPEG fail. "); return; } #ifdef USE_SHELL_OPEN browse(saveFile); #endif } void splitpath(const char *path, char *drv, char *dir, char *name, char *ext) { const char *end; const char *p; const char *s; if (path[0] && path[1] == ':') { if (drv) { *drv++ = *path++; *drv++ = *path++; *drv = ' '; } } else if (drv) *drv = ' '; for (end = path; *end && *end != ':';) end++; for (p = end; p > path && *--p != '\' && *p != '/';) if (*p == '.') { end = p; break; } if (ext) for (s = end; (*ext = *s++);) ext++; for (p = end; p > path;) if (*--p == '\' || *p == '/') { p++; break; } if (name) { for (s = p; s < end;) *name++ = *s++; *name = ' '; } if (dir) { for (s = path; s < p;) *dir++ = *s++; *dir = ' '; } } void getCurrentFilePath(const char *filePath, char *saveFile) { char drive[_MAX_DRIVE]; char dir[_MAX_DIR]; char fname[_MAX_FNAME]; char ext[_MAX_EXT]; splitpath(filePath, drive, dir, fname, ext); size_t n = strlen(filePath); memcpy(saveFile, filePath, n); char *cur_saveFile = saveFile + (n - strlen(ext)); cur_saveFile[0] = '_'; cur_saveFile[1] = 0; } int main(int argc, char **argv) { printf("lut 3d demo "); printf("blog:http://cpuimage.cnblogs.com/ "); if (argc < 3) { printf("usage: %s 3dlut image ", argv[0]); printf("eg: %s 3DLUT d:\image.jpg ", argv[0]); return (0); } char *lutfile = argv[1]; char *szfile = argv[2]; getCurrentFilePath(szfile, saveFile); int Width = 0; int Height = 0; int Channels = 0; unsigned char *inputImage = NULL; double startTime = now(); inputImage = loadImage(szfile, &Width, &Height, &Channels); double nLoadTime = calcElapsed(startTime, now()); printf("load time: %d ms. ", (int) (nLoadTime * 1000)); if ((Channels != 0) && (Width != 0) && (Height != 0)) { unsigned char *outputImg = (unsigned char *) stbi__malloc(Width * Channels * Height * sizeof(unsigned char)); if (inputImage) { memcpy(outputImg, inputImage, Width * Channels * Height); } else { printf("load: %s fail! ", szfile); } startTime = now(); int is16bit = 0; // INTERPOLATE_NEAREST // INTERPOLATE_TRILINEAR // INTERPOLATE_TETRAHEDRAL int interp_mode = INTERPOLATE_TETRAHEDRAL; apply_lut(lutfile, inputImage, outputImg, Width, Height, Width * Channels, Channels, interp_mode, is16bit); double nProcessTime = calcElapsed(startTime, now()); printf("process time: %d ms. ", (int) (nProcessTime * 1000)); startTime = now(); saveImage("_done.jpg", Width, Height, Channels, outputImg); double nSaveTime = calcElapsed(startTime, now()); printf("save time: %d ms. ", (int) (nSaveTime * 1000)); if (outputImg) { stbi_image_free(outputImg); } if (inputImage) { stbi_image_free(inputImage); } } else { printf("load: %s fail! ", szfile); } getchar(); printf("press any key to exit. "); return (EXIT_SUCCESS); }
项目地址:
https://github.com/cpuimage/Lut3D
命令行参数:
lut3d 3d预设文件 图片路径
例如: lut3d ../god.cube ../sample.jpg
用cmake即可进行编译示例代码，详情见CMakeLists.txt。
算法细节就不展开说了，
若有其他相关问题或者需求也可以邮件联系俺探讨。
邮箱地址是:
gaozhihan@vip.qq.com