Add custom kernels

Functionality is about the same as in Akarin's fork, but it's implemented in a different way internally.

Also added force/force_h/force_v paramenters to force sampling even if the resolution stays the same.

Only supported in the VapourSynth plugin.

Author: Frechdachs

README.md

@@ -10,22 +10,37 @@ The VapourSynth plugin itself supports every constant input format. If the forma
 The included python wrapper, contrary to using the plugin directly, doesn't descale the chroma planes but scales them normally with `Spline36`.
 
 ```
-descale.Debilinear(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Debilinear(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Debicubic(clip src, int width, int height, float b=0.0, float c=0.5, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Debicubic(clip src, int width, int height, float b=0.0, float c=0.5, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Delanczos(clip src, int width, int height, int taps=3, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Delanczos(clip src, int width, int height, int taps=3, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Despline16(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Despline16(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Despline36(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Despline36(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Despline64(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Despline64(clip src, int width, int height, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 
-descale.Descale(clip src, int width, int height, str kernel, int taps=3, float b=0.0, float c=0.0, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, int opt=0)
+descale.Descale(clip src, int width, int height, str kernel, func custom_kernel, int taps=3, float b=0.0, float c=0.0, float src_left=0.0, float src_top=0.0, float src_width=width, float src_height=height, bool force, bool force_h, bool force_v, int opt=0)
 ```
 
 The AviSynth+ plugin is used similarly, but without the `descale` namespace.
+Custom kernels are only supported in the VapourSynth plugin.
+
+### Custom kernels
+
+```python
+# Debilinear
+core.descale.Descale(src, w, h, custom_kernel=lambda x: 1.0 - x, taps=1)
+
+# Delanczos
+import math
+def sinc(x):
+	return 1.0 if x == 0 else math.sin(x * math.pi) / (x * math.pi)
+taps = 3
+core.descale.Descale(src, w, h, custom_kernel=lambda x: sinc(x) * sinc(x / taps), taps=taps)
+```
 
 ## How does this work?
 

descale.py

@@ -22,7 +22,7 @@ def Despline64(src, width, height, yuv444=False, gray=False, chromaloc=None):
     return Descale(src, width, height, kernel='spline64', taps=None, b=None, c=None, yuv444=yuv444, gray=gray, chromaloc=chromaloc)
 
 
-def Descale(src, width, height, kernel='bilinear', taps=3, b=0.0, c=0.5, yuv444=False, gray=False, chromaloc=None):
+def Descale(src, width, height, kernel=None, custom_kernel=None, taps=None, b=None, c=None, yuv444=False, gray=False, chromaloc=None):
     src_f = src.format
     src_cf = src_f.color_family
     src_st = src_f.sample_type
@@ -31,10 +31,10 @@ def Descale(src, width, height, kernel='bilinear', taps=3, b=0.0, c=0.5, yuv444=
     src_sh = src_f.subsampling_h
 
     if src_cf == RGB and not gray:
-        rgb = to_rgbs(src).descale.Descale(width, height, kernel, taps, b, c)
+        rgb = to_rgbs(src).descale.Descale(width, height, kernel, custom_kernel, taps, b, c)
         return rgb.resize.Point(format=src_f.id)
 
-    y = to_grays(src).descale.Descale(width, height, kernel, taps, b, c)
+    y = to_grays(src).descale.Descale(width, height, kernel, custom_kernel, taps, b, c)
     y_f = core.register_format(GRAY, src_st, src_bits, 0, 0)
     y = y.resize.Point(format=y_f.id)
 

include/descale.h

@@ -32,7 +32,8 @@ typedef enum DescaleMode
     DESCALE_MODE_LANCZOS  = 3,
     DESCALE_MODE_SPLINE16 = 4,
     DESCALE_MODE_SPLINE36 = 5,
-    DESCALE_MODE_SPLINE64 = 6
+    DESCALE_MODE_SPLINE64 = 6,
+    DESCALE_MODE_CUSTOM   = 7
 } DescaleMode;
 
 
@@ -51,15 +52,23 @@ typedef enum DescaleOpt
 } DescaleOpt;
 
 
+typedef struct DescaleCustomKernel
+{
+    double (*f)(double x, void *user_data);
+    void *user_data;
+} DescaleCustomKernel;
+
+
 // Optional struct members should be initialized to 0 if not used
 typedef struct DescaleParams
 {
     enum DescaleMode mode;
-    int taps;           // required if mode is LANCZOS
+    int taps;           // required if mode is LANCZOS or CUSTOM
     double param1;      // required if mode is BICUBIC
     double param2;      // required if mode is BICUBIC
     double shift;       // optional
     double active_dim;  // always required; usually equal to dst_dim
+    DescaleCustomKernel custom_kernel;  // required if mode is CUSTOM
 } DescaleParams;
 
 

meson.build

@@ -1,7 +1,7 @@
 project('Descale', 'c',
     default_options: ['buildtype=release', 'b_ndebug=if-release', 'c_std=c99'],
     meson_version: '>=0.51.0',
-    version: '7'
+    version: '8'
 )
 
 add_global_arguments(['-D_XOPEN_SOURCE=700'], language: 'c')
@@ -47,12 +47,19 @@ if host_machine.system() == 'windows'
 else
     m_dep = cc.find_library('m', required: false)
     p_dep = cc.find_library('pthread')
-    vs = dependency('vapoursynth').partial_dependency(compile_args: true, includes: true)
-    deps += [m_dep, p_dep, vs]
+    deps += [m_dep, p_dep]
+    if libtype in ['vapoursynth', 'both']
+        vs = dependency('vapoursynth').partial_dependency(compile_args: true, includes: true)
+        deps += [vs]
+    endif
+    if libtype in ['avisynth', 'both']
+        avs = dependency('avisynth')
+        deps += [avs]
+    endif
     if libtype in ['vapoursynth', 'both']
         installdir = join_paths(vs.get_pkgconfig_variable('libdir'), 'vapoursynth')
     else
-        installdir = join_paths(vs.get_pkgconfig_variable('libdir'), 'avisynth')
+        installdir = join_paths(avs.get_pkgconfig_variable('libdir'), 'avisynth')
     endif
 endif
 

src/avsplugin.c

@@ -245,8 +245,7 @@ static AVS_Value AVSC_CC avs_descale_create(AVS_ScriptEnvironment *env, AVS_Valu
         b = avs_defined(v) ? avs_as_float(v) : 0.0;
         v = avs_array_elt(args, idx++);
         c = avs_defined(v) ? avs_as_float(v) : 0.5;
-    }
-    else {
+    } else {
         b = 0.0;
         c = 0.5;
     }
@@ -263,6 +262,11 @@ static AVS_Value AVSC_CC avs_descale_create(AVS_ScriptEnvironment *env, AVS_Valu
     bool process_h = dst_width != src_width || shift_h != 0.0 || active_width != (double)dst_width;
     bool process_v = dst_height != src_height || shift_v != 0.0 || active_height != (double)dst_height;
 
+    if (!process_h && !process_v) {
+        v = avs_new_value_clip(clip);
+        goto done;
+    }
+
     v = avs_array_elt(args, idx++);
     int opt = avs_defined(v) ? avs_as_int(v) : 0;
     enum DescaleOpt opt_enum;
@@ -277,7 +281,7 @@ static AVS_Value AVSC_CC avs_descale_create(AVS_ScriptEnvironment *env, AVS_Valu
     if (bytes_per_pixel != 4) {
         AVS_Value c2, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11;
         c1 = avs_new_value_clip(clip);
-        //avs_release_clip(clip);  // This is apparently wrong, leaving it uncommented crashes sometimes
+        avs_release_clip(clip);
         a1 = avs_new_value_int(32);
         AVS_Value convert_args[] = {c1, a1};
         c2 = avs_invoke(env, "ConvertBits", avs_new_value_array(convert_args, 2), NULL);

src/descale.c

@@ -163,7 +163,7 @@ static inline double cube(double x)
 }
 
 
-static double calculate_weight(enum DescaleMode mode, int support, double distance, double b, double c)
+static double calculate_weight(enum DescaleMode mode, int support, double distance, double b, double c, struct DescaleCustomKernel *ck)
 {
     distance = fabs(distance);
 
@@ -221,6 +221,8 @@ static double calculate_weight(enum DescaleMode mode, int support, double distan
         } else {
             return 0.0;
         }
+    } else if (mode == DESCALE_MODE_CUSTOM) {
+        return ck->f(distance, ck->user_data);
     }
 
     return 0.0;
@@ -242,7 +244,7 @@ static double round_halfup(double x)
 
 // Most of this is taken from zimg 
 // https://github.com/sekrit-twc/zimg/blob/ce27c27f2147fbb28e417fbf19a95d3cf5d68f4f/src/zimg/resize/filter.cpp#L227
-static void scaling_weights(enum DescaleMode mode, int support, int src_dim, int dst_dim, double param1, double param2, double shift, double active_dim, double **weights)
+static void scaling_weights(enum DescaleMode mode, int support, int src_dim, int dst_dim, double param1, double param2, double shift, double active_dim, struct DescaleCustomKernel *ck, double **weights)
 {
     *weights = calloc(src_dim * dst_dim, sizeof (double));
     double ratio = (double)dst_dim / active_dim;
@@ -254,7 +256,7 @@ static void scaling_weights(enum DescaleMode mode, int support, int src_dim, int
         double begin_pos = round_halfup(pos - support) + 0.5;
         for (int j = 0; j < 2 * support; j++) {
             double xpos = begin_pos + j;
-            total += calculate_weight(mode, support, xpos - pos, param1, param2);
+            total += calculate_weight(mode, support, xpos - pos, param1, param2, ck);
         }
         for (int j = 0; j < 2 * support; j++) {
             double xpos = begin_pos + j;
@@ -269,7 +271,7 @@ static void scaling_weights(enum DescaleMode mode, int support, int src_dim, int
                 real_pos = xpos;
 
             int idx = (int)floor(real_pos);
-            (*weights)[i * src_dim + idx] += calculate_weight(mode, support, xpos - pos, param1, param2) / total;
+            (*weights)[i * src_dim + idx] += calculate_weight(mode, support, xpos - pos, param1, param2, ck) / total;
         }
     }
 }
@@ -561,18 +563,21 @@ static struct DescaleCore *create_core(int src_dim, int dst_dim, struct DescaleP
         support = 2;
     } else if (params->mode == DESCALE_MODE_LANCZOS) {
         support = params->taps;
-        if (support == 0)
-            return NULL;
     } else if (params->mode == DESCALE_MODE_SPLINE16) {
         support = 2;
     } else if (params->mode == DESCALE_MODE_SPLINE36) {
         support = 3;
     } else if (params->mode == DESCALE_MODE_SPLINE64) {
         support = 4;
+    } else if (params->mode == DESCALE_MODE_CUSTOM) {
+        support = params->taps;
     } else {
         return NULL;
     }
 
+    if (support == 0)
+        return NULL;
+
     core.src_dim = src_dim;
     core.dst_dim = dst_dim;
     core.bandwidth = support * 4 - 1;
@@ -582,7 +587,7 @@ static struct DescaleCore *create_core(int src_dim, int dst_dim, struct DescaleP
     double *multiplied_weights;
     double *lower;
 
-    scaling_weights(params->mode, support, dst_dim, src_dim, params->param1, params->param2, params->shift, params->active_dim, &weights);
+    scaling_weights(params->mode, support, dst_dim, src_dim, params->param1, params->param2, params->shift, params->active_dim, &params->custom_kernel, &weights);
     transpose_matrix(src_dim, dst_dim, weights, &transposed_weights);
 
     core.weights_left_idx = calloc(ceil_n(dst_dim, 8), sizeof (int));