Alphablend changes

shared-bindings/bitmaptools/__init__.c

@@ -273,6 +273,28 @@ STATIC mp_obj_t bitmaptools_obj_rotozoom(size_t n_args, const mp_obj_t *pos_args
 }
 
 MP_DEFINE_CONST_FUN_OBJ_KW(bitmaptools_rotozoom_obj, 0, bitmaptools_obj_rotozoom);
+
+MAKE_ENUM_VALUE(bitmaptools_blendmode_type, bitmaptools_blendmode, NORMAL, BITMAPTOOLS_BLENDMODE_NORMAL);
+MAKE_ENUM_VALUE(bitmaptools_blendmode_type, bitmaptools_blendmode, SCREEN, BITMAPTOOLS_BLENDMODE_SCREEN);
+
+//| class BlendMode:
+//|     """The blend mode for `alphablend` to operate use"""
+//|
+//|     NORMAL: Blendmode
+//|     """Blend with equal parts of the two source bitmaps"""
+//|
+//|     SCREEN: Blendmode
+//|     """Blend based on the value in each color channel. The result keeps the lighter colors and discards darker colors."""
+//|
+MAKE_ENUM_MAP(bitmaptools_blendmode) {
+    MAKE_ENUM_MAP_ENTRY(bitmaptools_blendmode, NORMAL),
+    MAKE_ENUM_MAP_ENTRY(bitmaptools_blendmode, SCREEN),
+};
+STATIC MP_DEFINE_CONST_DICT(bitmaptools_blendmode_locals_dict, bitmaptools_blendmode_locals_table);
+
+MAKE_PRINTER(bitmaptools, bitmaptools_blendmode);
+MAKE_ENUM_TYPE(bitmaptools, BlendMode, bitmaptools_blendmode);
+
 // requires at least 2 arguments (destination bitmap and source bitmap)
 
 //| def alphablend(
@@ -282,6 +304,9 @@ MP_DEFINE_CONST_FUN_OBJ_KW(bitmaptools_rotozoom_obj, 0, bitmaptools_obj_rotozoom
 //|     colorspace: displayio.Colorspace,
 //|     factor1: float = 0.5,
 //|     factor2: Optional[float] = None,
+//|     blendmode: Optional[Blendmode] = Blendmode.NORMAL,
+//|     skip_source1_index: int,
+//|     skip_source2_index: int,
 //| ) -> None:
 //|     """Alpha blend the two source bitmaps into the destination.
 //|
@@ -294,13 +319,18 @@ MP_DEFINE_CONST_FUN_OBJ_KW(bitmaptools_rotozoom_obj, 0, bitmaptools_obj_rotozoom
 //|     :param float factor1: The proportion of bitmap 1 to mix in
 //|     :param float factor2: The proportion of bitmap 2 to mix in.  If specified as `None`, ``1-factor1`` is used.  Usually the proportions should sum to 1.
 //|     :param displayio.Colorspace colorspace: The colorspace of the bitmaps. They must all have the same colorspace.  Only the following colorspaces are permitted:  ``L8``, ``RGB565``, ``RGB565_SWAPPED``, ``BGR565`` and ``BGR565_SWAPPED``.
+//|     :param bitmaptools.BlendMode blendmode: The blend mode to use. Default is NORMAL.
+//|     :param int skip_source1_index: bitmap palette index in the source that will not be blended,
+//|                            set to None to blended all pixels
+//|     :param int skip_source2_index: bitmap palette index in the source that will not be blended,
+//|                            set to None to blended all pixels
 //|
 //|     For the L8 colorspace, the bitmaps must have a bits-per-value of 8.
 //|     For the RGB colorspaces, they must have a bits-per-value of 16."""
 //|
 
 STATIC mp_obj_t bitmaptools_alphablend(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    enum {ARG_dest_bitmap, ARG_source_bitmap_1, ARG_source_bitmap_2, ARG_colorspace, ARG_factor_1, ARG_factor_2};
+    enum {ARG_dest_bitmap, ARG_source_bitmap_1, ARG_source_bitmap_2, ARG_colorspace, ARG_factor_1, ARG_factor_2, ARG_blendmode, ARG_skip_source1_index, ARG_skip_source2_index};
 
     static const mp_arg_t allowed_args[] = {
         {MP_QSTR_dest_bitmap, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = NULL}},
@@ -309,6 +339,9 @@ STATIC mp_obj_t bitmaptools_alphablend(size_t n_args, const mp_obj_t *pos_args,
         {MP_QSTR_colorspace, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = NULL}},
         {MP_QSTR_factor_1, MP_ARG_OBJ, {.u_obj = MP_ROM_NONE}},
         {MP_QSTR_factor_2, MP_ARG_OBJ, {.u_obj = MP_ROM_NONE}},
+        {MP_QSTR_blendmode, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = (void *)&bitmaptools_blendmode_NORMAL_obj}},
+        {MP_QSTR_skip_source1_index, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_none} },
+        {MP_QSTR_skip_source2_index, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_none} },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
@@ -321,6 +354,7 @@ STATIC mp_obj_t bitmaptools_alphablend(size_t n_args, const mp_obj_t *pos_args,
     mp_float_t factor2 = (args[ARG_factor_2].u_obj == mp_const_none) ? 1 - factor1 : mp_obj_get_float(args[ARG_factor_2].u_obj);
 
     displayio_colorspace_t colorspace = (displayio_colorspace_t)cp_enum_value(&displayio_colorspace_type, args[ARG_colorspace].u_obj, MP_QSTR_colorspace);
+    bitmaptools_blendmode_t blendmode = (bitmaptools_blendmode_t)cp_enum_value(&bitmaptools_blendmode_type, args[ARG_blendmode].u_obj, MP_QSTR_blendmode);
 
     if (destination->width != source1->width
         || destination->height != source1->height
@@ -352,7 +386,30 @@ STATIC mp_obj_t bitmaptools_alphablend(size_t n_args, const mp_obj_t *pos_args,
             mp_raise_ValueError(translate("Unsupported colorspace"));
     }
 
-    common_hal_bitmaptools_alphablend(destination, source1, source2, colorspace, factor1, factor2);
+    uint32_t skip_source1_index;
+    bool skip_source1_index_none; // flag whether skip_value was None
+
+    if (args[ARG_skip_source1_index].u_obj == mp_const_none) {
+        skip_source1_index = 0;
+        skip_source1_index_none = true;
+    } else {
+        skip_source1_index = mp_obj_get_int(args[ARG_skip_source1_index].u_obj);
+        skip_source1_index_none = false;
+    }
+
+    uint32_t skip_source2_index;
+    bool skip_source2_index_none; // flag whether skip_self_value was None
+
+    if (args[ARG_skip_source2_index].u_obj == mp_const_none) {
+        skip_source2_index = 0;
+        skip_source2_index_none = true;
+    } else {
+        skip_source2_index = mp_obj_get_int(args[ARG_skip_source2_index].u_obj);
+        skip_source2_index_none = false;
+    }
+
+    common_hal_bitmaptools_alphablend(destination, source1, source2, colorspace, factor1, factor2, blendmode, skip_source1_index,
+        skip_source1_index_none, skip_source2_index, skip_source2_index_none);
 
     return mp_const_none;
 }
@@ -1080,6 +1137,7 @@ STATIC const mp_rom_map_elem_t bitmaptools_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&bitmaptools_readinto_obj) },
     { MP_ROM_QSTR(MP_QSTR_rotozoom), MP_ROM_PTR(&bitmaptools_rotozoom_obj) },
     { MP_ROM_QSTR(MP_QSTR_arrayblit), MP_ROM_PTR(&bitmaptools_arrayblit_obj) },
+    { MP_ROM_QSTR(MP_QSTR_Blendmode), MP_ROM_PTR(&bitmaptools_blendmode_type) },
     { MP_ROM_QSTR(MP_QSTR_alphablend), MP_ROM_PTR(&bitmaptools_alphablend_obj) },
     { MP_ROM_QSTR(MP_QSTR_fill_region), MP_ROM_PTR(&bitmaptools_fill_region_obj) },
     { MP_ROM_QSTR(MP_QSTR_boundary_fill), MP_ROM_PTR(&bitmaptools_boundary_fill_obj) },

shared-bindings/bitmaptools/__init__.h

@@ -40,6 +40,11 @@ typedef enum {
 
 extern const mp_obj_type_t bitmaptools_dither_algorithm_type;
 
+typedef enum bitmaptools_blendmode {
+    BITMAPTOOLS_BLENDMODE_NORMAL,
+    BITMAPTOOLS_BLENDMODE_SCREEN,
+} bitmaptools_blendmode_t;
+
 void common_hal_bitmaptools_rotozoom(displayio_bitmap_t *self, int16_t ox, int16_t oy,
     int16_t dest_clip0_x, int16_t dest_clip0_y,
     int16_t dest_clip1_x, int16_t dest_clip1_y,
@@ -78,6 +83,10 @@ void common_hal_bitmaptools_readinto(displayio_bitmap_t *self, mp_obj_t *file, i
 void common_hal_bitmaptools_arrayblit(displayio_bitmap_t *self, void *data, int element_size, int x1, int y1, int x2, int y2, bool skip_specified, uint32_t skip_index);
 void common_hal_bitmaptools_dither(displayio_bitmap_t *dest_bitmap, displayio_bitmap_t *source_bitmap, displayio_colorspace_t colorspace, bitmaptools_dither_algorithm_t algorithm);
 
-void common_hal_bitmaptools_alphablend(displayio_bitmap_t *destination, displayio_bitmap_t *source1, displayio_bitmap_t *source2, displayio_colorspace_t colorspace, mp_float_t factor1, mp_float_t factor2);
+void common_hal_bitmaptools_alphablend(displayio_bitmap_t *destination, displayio_bitmap_t *source1, displayio_bitmap_t *source2, displayio_colorspace_t colorspace, mp_float_t factor1, mp_float_t factor2,
+    bitmaptools_blendmode_t blendmode, uint32_t skip_source1_index, bool skip_source1_index_none, uint32_t skip_source2_index, bool skip_source2_index_none);
+
+extern const mp_obj_type_t bitmaptools_blendmode_type;
+extern const cp_enum_obj_t bitmaptools_blendmode_NORMAL_obj;
 
 #endif // MICROPY_INCLUDED_SHARED_BINDINGS_BITMAPTOOLS__INIT__H

shared-module/bitmaptools/__init__.c

@@ -861,26 +861,53 @@ void common_hal_bitmaptools_dither(displayio_bitmap_t *dest_bitmap, displayio_bi
     displayio_bitmap_set_dirty_area(dest_bitmap, &a);
 }
 
-void common_hal_bitmaptools_alphablend(displayio_bitmap_t *dest, displayio_bitmap_t *source1, displayio_bitmap_t *source2, displayio_colorspace_t colorspace, mp_float_t factor1, mp_float_t factor2) {
+void common_hal_bitmaptools_alphablend(displayio_bitmap_t *dest, displayio_bitmap_t *source1, displayio_bitmap_t *source2, displayio_colorspace_t colorspace, mp_float_t factor1, mp_float_t factor2,
+    bitmaptools_blendmode_t blendmode, uint32_t skip_source1_index, bool skip_source1_index_none, uint32_t skip_source2_index, bool skip_source2_index_none) {
     displayio_area_t a = {0, 0, dest->width, dest->height, NULL};
     displayio_bitmap_set_dirty_area(dest, &a);
 
     int ifactor1 = (int)(factor1 * 256);
     int ifactor2 = (int)(factor2 * 256);
+    bool blend_source1, blend_source2;
 
     if (colorspace == DISPLAYIO_COLORSPACE_L8) {
         for (int y = 0; y < dest->height; y++) {
             uint8_t *dptr = (uint8_t *)(dest->data + y * dest->stride);
             uint8_t *sptr1 = (uint8_t *)(source1->data + y * source1->stride);
             uint8_t *sptr2 = (uint8_t *)(source2->data + y * source2->stride);
+            int pixel;
             for (int x = 0; x < dest->width; x++) {
-                // This is round(l1*f1 + l2*f2) & clip to range in fixed-point
+                blend_source1 = skip_source1_index_none || *sptr1 != (uint8_t)skip_source1_index;
-                int pixel = (*sptr1++ *ifactor1 + *sptr2++ *ifactor2 + 128) / 256;
+                blend_source2 = skip_source2_index_none || *sptr2 != (uint8_t)skip_source2_index;
+                if (blend_source1 && blend_source2) {
+                    // Premultiply by the alpha factor
+                    int sca1 = *sptr1++ * ifactor1;
+                    int sca2 = *sptr2++ * ifactor2;
+                    // Blend
+                    int blend;
+                    if (blendmode == BITMAPTOOLS_BLENDMODE_SCREEN) {
+                        blend = sca2 + sca1 - sca2 * sca1;
+                    } else {
+                        blend = sca2 + sca1 * (256 - ifactor2);
+                    }
+                    // Divide by the alpha factor
+                    pixel = (blend / (256 * ifactor1 + 256 * ifactor2 - ifactor1 * ifactor2));
+                } else if (blend_source1) {
+                    // Apply iFactor1 to source1 only
+                    pixel = *sptr1++ *ifactor1 / 256;
+                } else if (blend_source2) {
+                    // Apply iFactor2 to source1 only
+                    pixel = *sptr2++ *ifactor2 / 256;
+                } else {
+                    // Use the destination value
+                    pixel = *dptr;
+                }
                 *dptr++ = MIN(255, MAX(0, pixel));
             }
         }
     } else {
         bool swap = (colorspace == DISPLAYIO_COLORSPACE_RGB565_SWAPPED) || (colorspace == DISPLAYIO_COLORSPACE_BGR565_SWAPPED);
+        uint16_t pixel;
         for (int y = 0; y < dest->height; y++) {
             uint16_t *dptr = (uint16_t *)(dest->data + y * dest->stride);
             uint16_t *sptr1 = (uint16_t *)(source1->data + y * source1->stride);
@@ -897,25 +924,63 @@ void common_hal_bitmaptools_alphablend(displayio_bitmap_t *dest, displayio_bitma
                 const int g_mask = 0x07e0;
                 const int b_mask = 0x001f; // (or r mask, if BGR)
 
-                // This is round(r1*f1 + r2*f2) & clip to range in fixed-point
+                blend_source1 = skip_source1_index_none || spix1 != (int)skip_source1_index;
-                // but avoiding shifting it down to start at bit 0
+                blend_source2 = skip_source2_index_none || spix2 != (int)skip_source2_index;
-                int r = ((spix1 & r_mask) * ifactor1
+
-                    + (spix2 & r_mask) * ifactor2 + r_mask / 2) / 256;
+                if (blend_source1 && blend_source2) {
+                    // Blend based on the SVG alpha compositing specs
+                    // https://dev.w3.org/SVG/modules/compositing/master/#alphaCompositing
+
+                    int ifactor_blend = ifactor1 + ifactor2 - ifactor1 * ifactor2 / 256;
+
+                    // Premultiply the colors by the alpha factor
+                    int red_sca1 = ((spix1 & r_mask) >> 11) * ifactor1;
+                    int green_sca1 = ((spix1 & g_mask) >> 5) * ifactor1;
+                    int blue_sca1 = (spix1 & b_mask) * ifactor1;
+
+                    int red_sca2 = ((spix2 & r_mask) >> 11) * ifactor2;
+                    int green_sca2 = ((spix2 & g_mask) >> 5) * ifactor2;
+                    int blue_sca2 = (spix2 & b_mask) * ifactor2;
+
+                    int red_blend, green_blend, blue_blend;
+                    if (blendmode == BITMAPTOOLS_BLENDMODE_SCREEN) {
+                        // Perform a screen blend
+                        red_blend = red_sca2 + red_sca1 - (red_sca2 * red_sca1);
+                        green_blend = green_sca2 + green_sca1 - (green_sca2 * green_sca1);
+                        blue_blend = blue_sca2 + blue_sca1 - (blue_sca2 * blue_sca1);
+                    } else {
+                        // Perform a normal blend
+                        red_blend = red_sca2 + red_sca1 * (256 - ifactor2) / 256;
+                        green_blend = green_sca2 + green_sca1 * (256 - ifactor2) / 256;
+                        blue_blend = blue_sca2 + blue_sca1 * (256 - ifactor2) / 256;
+                    }
+
+                    // Divide by the alpha factor
+                    int r = ((red_blend / ifactor_blend) << 11) & r_mask;
+                    int g = ((green_blend / ifactor_blend) << 5) & g_mask;
+                    int b = (blue_blend / ifactor_blend) & b_mask;
+
+                    // Clamp to the appropriate range
                     r = MIN(r_mask, MAX(0, r)) & r_mask;
-
-                // ditto
-                int g = ((spix1 & g_mask) * ifactor1
-                    + (spix2 & g_mask) * ifactor2 + g_mask / 2) / 256;
                     g = MIN(g_mask, MAX(0, g)) & g_mask;
-
-                int b = ((spix1 & b_mask) * ifactor1
-                    + (spix2 & b_mask) * ifactor2 + b_mask / 2) / 256;
                     b = MIN(b_mask, MAX(0, b)) & b_mask;
 
-                uint16_t pixel = r | g | b;
+                    pixel = r | g | b;
+
                     if (swap) {
                         pixel = __builtin_bswap16(pixel);
                     }
+                } else if (blend_source1) {
+                    // Apply iFactor1 to source1 only
+                    pixel = spix1 * ifactor1 / 256;
+                } else if (blend_source2) {
+                    // Apply iFactor2 to source1 only
+                    pixel = spix2 * ifactor2 / 256;
+                } else {
+                    // Use the destination value
+                    pixel = *dptr;
+                }
+
                 *dptr++ = pixel;
             }
         }