Don't convert sampled color back and forth

It got sampled as a float, turned into a 15 bit color only to be
converted back into a float. Now it just stays a float.

extern/drawdance/libengine/dpengine/brush_engine.c

@@ -596,13 +596,13 @@ static void get_color_mypaint_pigment(MyPaintSurface2 *self, float x, float y,
     DP_LayerContent *lc = be->lc;
     if (lc) {
         int diameter = DP_min_int(DP_float_to_int(radius * 2.0f + 0.5f), 255);
-        DP_UPixel15 color = DP_layer_content_sample_color_at(
+        DP_UPixelFloat color = DP_layer_content_sample_color_at(
             lc, be->stamp_buffer, DP_float_to_int(x + 0.5f),
             DP_float_to_int(y + 0.5f), diameter, &be->last_diameter);
-        *color_r = DP_channel15_to_float(color.r);
-        *color_g = DP_channel15_to_float(color.g);
-        *color_b = DP_channel15_to_float(color.b);
-        *color_a = DP_channel15_to_float(color.a);
+        *color_r = color.r;
+        *color_g = color.g;
+        *color_b = color.b;
+        *color_a = color.a;
     }
     else {
         *color_r = 0.0f;
@@ -940,9 +940,9 @@ static DP_UPixelFloat sample_classic_smudge(DP_BrushEngine *be,
                                             float y, float pressure)
 {
     int diameter = get_classic_smudge_diameter(cb, pressure);
-    return DP_upixel15_to_float(DP_layer_content_sample_color_at(
+    return DP_layer_content_sample_color_at(
         lc, be->stamp_buffer, DP_float_to_int(x), DP_float_to_int(y), diameter,
-        &be->last_diameter));
+        &be->last_diameter);
 }
 
 static void update_classic_smudge(DP_BrushEngine *be, DP_ClassicBrush *cb,

extern/drawdance/libengine/dpengine/layer_content.c

@@ -355,7 +355,7 @@ bool DP_layer_content_pick_at(DP_LayerContent *lc, int x, int y,
     return false;
 }
 
-static DP_UPixel15 sample_dab_color(DP_LayerContent *lc, DP_BrushStamp stamp)
+static DP_UPixelFloat sample_dab_color(DP_LayerContent *lc, DP_BrushStamp stamp)
 {
     uint16_t *weights = stamp.data;
     int diameter = stamp.diameter;
@@ -405,7 +405,7 @@ static DP_UPixel15 sample_dab_color(DP_LayerContent *lc, DP_BrushStamp stamp)
     float required_alpha =
         DP_int_to_float(DP_square_int(diameter) * 30) / (float)DP_BIT15;
     if (alpha < required_alpha) {
-        return DP_upixel15_zero();
+        return DP_upixel_float_zero();
     }
 
     // Calculate final average
@@ -419,23 +419,23 @@ static DP_UPixel15 sample_dab_color(DP_LayerContent *lc, DP_BrushStamp stamp)
     green = CLAMP(green / alpha, 0.0f, 1.0f);
     blue = CLAMP(blue / alpha, 0.0f, 1.0f);
 
-    return (DP_UPixel15){
-        .b = DP_channel_float_to_15(blue),
-        .g = DP_channel_float_to_15(green),
-        .r = DP_channel_float_to_15(red),
-        .a = DP_channel_float_to_15(alpha),
+    return (DP_UPixelFloat){
+        .b = blue,
+        .g = green,
+        .r = red,
+        .a = alpha,
     };
 }
 
-DP_UPixel15 DP_layer_content_sample_color_at(DP_LayerContent *lc,
-                                             uint16_t *stamp_buffer, int x,
-                                             int y, int diameter,
-                                             int *in_out_last_diameter)
+DP_UPixelFloat DP_layer_content_sample_color_at(DP_LayerContent *lc,
+                                                uint16_t *stamp_buffer, int x,
+                                                int y, int diameter,
+                                                int *in_out_last_diameter)
 {
     if (x >= 0 && y >= 0 && x < lc->width && y < lc->height) {
         if (diameter < 2) {
             DP_Pixel15 pixel = DP_layer_content_pixel_at(lc, x, y);
-            return DP_pixel15_unpremultiply(pixel);
+            return DP_upixel15_to_float(DP_pixel15_unpremultiply(pixel));
         }
         else {
             int last_diameter;
@@ -452,7 +452,7 @@ DP_UPixel15 DP_layer_content_sample_color_at(DP_LayerContent *lc,
         }
     }
     else {
-        return DP_upixel15_zero();
+        return DP_upixel_float_zero();
     }
 }
 

extern/drawdance/libengine/dpengine/layer_content.h

@@ -84,10 +84,10 @@ DP_Pixel15 DP_layer_content_pixel_at(DP_LayerContent *lc, int x, int y);
 bool DP_layer_content_pick_at(DP_LayerContent *lc, int x, int y,
                               unsigned int *out_context_id);
 
-DP_UPixel15 DP_layer_content_sample_color_at(DP_LayerContent *lc,
-                                             uint16_t *stamp_buffer, int x,
-                                             int y, int diameter,
-                                             int *in_out_last_diameter);
+DP_UPixelFloat DP_layer_content_sample_color_at(DP_LayerContent *lc,
+                                                uint16_t *stamp_buffer, int x,
+                                                int y, int diameter,
+                                                int *in_out_last_diameter);
 
 DP_LayerList *DP_layer_content_sub_contents_noinc(DP_LayerContent *lc);
 

extern/drawdance/libengine/dpengine/pixels.h

@@ -89,6 +89,7 @@ DP_UPixel15 DP_upixel8_to_15(DP_UPixel8 pixel);
 DP_UPixel8 DP_upixel15_to_8(DP_UPixel15 pixel);
 DP_UPixelFloat DP_upixel8_to_float(DP_UPixel8 pixel);
 DP_UPixelFloat DP_upixel15_to_float(DP_UPixel15 pixel);
+DP_UPixelFloat DP_upixel15_to_float_round(DP_UPixel15 pixel);
 DP_UPixel8 DP_upixel_float_to_8(DP_UPixelFloat pixel);
 
 void DP_pixels8_to_15(DP_Pixel15 *dst, const DP_Pixel8 *src, int count);
@@ -132,6 +133,12 @@ DP_INLINE DP_UPixel15 DP_upixel15_from_color(uint32_t color)
     return DP_upixel8_to_15(pixel);
 }
 
+DP_INLINE DP_UPixelFloat DP_upixel_float_zero(void)
+{
+    DP_UPixelFloat pixel = {0.0f, 0.0f, 0.0f, 0.0f};
+    return pixel;
+}
+
 DP_INLINE DP_UPixelFloat DP_upixel_float_from_color(uint32_t color)
 {
     DP_UPixel8 pixel = {color};

src/libclient/drawdance/layercontent.cpp

@@ -68,11 +68,11 @@ bool LayerContent::isNull() const
 QColor LayerContent::sampleColorAt(
     uint16_t *stampBuffer, int x, int y, int diameter, int &lastDiameter) const
 {
-    DP_UPixel15 pixel = DP_layer_content_sample_color_at(
+    DP_UPixelFloat pixel = DP_layer_content_sample_color_at(
         m_data, stampBuffer, x, y, diameter, &lastDiameter);
-    return QColor{
-        DP_channel15_to_8(pixel.r), DP_channel15_to_8(pixel.g),
-        DP_channel15_to_8(pixel.b), DP_channel15_to_8(pixel.a)};
+    QColor color;
+    color.setRgbF(pixel.r, pixel.g, pixel.b, pixel.a);
+    return color;
 }
 
 QImage LayerContent::toImage(const QRect &rect) const