diff options
Diffstat (limited to 'shared-module/displayio/Bitmap.c')
| -rw-r--r-- | shared-module/displayio/Bitmap.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/shared-module/displayio/Bitmap.c b/shared-module/displayio/Bitmap.c index 453dc1c59..addc341a7 100644 --- a/shared-module/displayio/Bitmap.c +++ b/shared-module/displayio/Bitmap.c @@ -31,8 +31,8 @@ #include "py/runtime.h" void common_hal_displayio_bitmap_construct(displayio_bitmap_t *self, uint32_t width, - uint32_t height, uint32_t value_size) { - uint32_t row_width = width * value_size; + uint32_t height, uint32_t bits_per_value) { + uint32_t row_width = width * bits_per_value; // word align if (row_width % 32 != 0) { self->stride = (row_width / 32 + 1); @@ -43,16 +43,25 @@ void common_hal_displayio_bitmap_construct(displayio_bitmap_t *self, uint32_t wi self->height = height; self->data = m_malloc(self->stride * height * sizeof(uint32_t), false); - self->bits_per_value = value_size; + self->bits_per_value = bits_per_value; - self->x_shift = 0; + if (bits_per_value > 8) { + mp_raise_NotImplementedError(translate("Only bit maps of 8 bit color or less are supported")); + } + + // Division and modulus can be slow because it has to handle any integer. We know bits_per_value + // is a power of two. We divide and mod by bits_per_value to compute the offset into the byte + // array. So, we can the offset computation to simplify to a shift for division and mask for mod. + + self->x_shift = 0; // Used to divide the index by the number of pixels per word. Its used in a + // shift which effectively divides by 2 ** x_shift. uint32_t power_of_two = 1; - while (power_of_two < 32 / value_size ) { + while (power_of_two < 32 / bits_per_value ) { self->x_shift++; power_of_two <<= 1; } self->x_mask = (1 << self->x_shift) - 1; // Used as a modulus on the x value - self->bitmask = (1 << value_size) - 1; + self->bitmask = (1 << bits_per_value) - 1; } void common_hal_displayio_bitmap_load_row(displayio_bitmap_t *self, uint16_t y, uint8_t* data, uint16_t len) { |