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_pixelbuf: Respond to review comments

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* Comment on the reason for scaling by 256
 * Divide by 256 instead of shifting
 * fix a cast; eliminate an unneeded roundf() to get a few bytes code back
This commit is contained in:
Jeff Epler 2021-02-24 16:27:09 -06:00
parent b7f5c277ad
commit dac4ac5d2a
1 changed files with 7 additions and 26 deletions
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33
shared-module/_pixelbuf/PixelBuf.c
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@ -112,7 +112,8 @@ void common_hal__pixelbuf_pixelbuf_set_brightness(mp_obj_t self_in, mp_float_t b
// Skip out if the brightness is already set. The default of self->brightness is 1.0. So, this
// also prevents the pre_brightness_buffer allocation when brightness is set to 1.0 again.
self->brightness = brightness;
uint16_t new_scaled_brightness = (int)roundf(brightness * 256);
// Use 256 steps of brightness so that we can do integer math below.
uint16_t new_scaled_brightness = (uint16_t)(brightness * 256);
if (new_scaled_brightness == self->scaled_brightness) {
return;
}
@ -130,7 +131,7 @@ void common_hal__pixelbuf_pixelbuf_set_brightness(mp_obj_t self_in, mp_float_t b
if (self->byteorder.is_dotstar && i % 4 == 0) {
continue;
}
self->post_brightness_buffer[i] = (self->pre_brightness_buffer[i] * self->scaled_brightness) >> 8;
self->post_brightness_buffer[i] = (self->pre_brightness_buffer[i] * self->scaled_brightness) / 256;
}
if (self->auto_write) {
@ -224,13 +225,13 @@ void _pixelbuf_set_pixel_color(pixelbuf_pixelbuf_obj_t* self, size_t index, uint
if (scaled_buffer) {
if (self->bytes_per_pixel == 4) {
if (!self->byteorder.is_dotstar) {
w = (w * self->scaled_brightness) >> 8;
w = (w * self->scaled_brightness) / 256;
}
scaled_buffer[rgbw_order->w] = w;
}
scaled_buffer[rgbw_order->r] = (r * self->scaled_brightness) >> 8;
scaled_buffer[rgbw_order->g] = (g * self->scaled_brightness) >> 8;
scaled_buffer[rgbw_order->b] = (b * self->scaled_brightness) >> 8;
scaled_buffer[rgbw_order->r] = (r * self->scaled_brightness) / 256;
scaled_buffer[rgbw_order->g] = (g * self->scaled_brightness) / 256;
scaled_buffer[rgbw_order->b] = (b * self->scaled_brightness) / 256;
}
}
@ -331,23 +332,3 @@ void common_hal__pixelbuf_pixelbuf_fill(mp_obj_t self_in, mp_obj_t fill_color) {
common_hal__pixelbuf_pixelbuf_show(self_in);
}
}
mp_int_t common_hal__pixelbuf_get_buffer(mp_obj_t self_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
pixelbuf_pixelbuf_obj_t *self = native_pixelbuf(self_in);
bufinfo->buf = self->pre_brightness_buffer;
if (self->pre_brightness_buffer) {
// If we have a brightness setting, we must treat the buffer as
// read-only (because we have no way to "fire" the
// brightness-converting code as a side effect of mutation via the
// buffer)
if ((flags & MP_BUFFER_WRITE)) {
return 1;
}
bufinfo->buf = self->pre_brightness_buffer;
} else {
bufinfo->buf = self->post_brightness_buffer;
}
bufinfo->typecode = 'B';
bufinfo->len = self->bytes_per_pixel * common_hal__pixelbuf_pixelbuf_get_len(self_in);
return 0;
}