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unroll vertical_upsample inner loop, and reverse loop nesting to minimize work

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This commit is contained in:
Sean Barrett 2014-09-13 07:41:39 -07:00
parent 9c2ae9bdb8
commit 7a8c9196d1
1 changed files with 76 additions and 15 deletions
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91
stb_image_resize.h
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@ -1703,6 +1703,7 @@ static void stbir__resample_vertical_upsample(stbir__info* stbir_info, int n, in
float* encode_buffer = stbir_info->encode_buffer;
int decode = STBIR__DECODE(type, colorspace);
int coefficient_width = stbir_info->vertical_coefficient_width;
int coefficient_counter;
int contributor = n;
float* ring_buffer = stbir_info->ring_buffer;
@ -1723,21 +1724,81 @@ static void stbir__resample_vertical_upsample(stbir__info* stbir_info, int n, in
memset(encode_buffer, 0, output_w * sizeof(float) * channels);
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
int coefficient_counter = 0;
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
int c;
for (c = 0; c < channels; c++)
encode_buffer[in_pixel_index + c] += ring_buffer_entry[in_pixel_index + c] * coefficient;
}
coefficient_counter = 0;
switch (channels) {
case 1:
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
}
}
break;
case 2:
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
}
}
break;
case 3:
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
encode_buffer[in_pixel_index + 2] += ring_buffer_entry[in_pixel_index + 2] * coefficient;
}
}
break;
case 4:
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
encode_buffer[in_pixel_index + 0] += ring_buffer_entry[in_pixel_index + 0] * coefficient;
encode_buffer[in_pixel_index + 1] += ring_buffer_entry[in_pixel_index + 1] * coefficient;
encode_buffer[in_pixel_index + 2] += ring_buffer_entry[in_pixel_index + 2] * coefficient;
encode_buffer[in_pixel_index + 3] += ring_buffer_entry[in_pixel_index + 3] * coefficient;
}
}
break;
default:
for (k = n0; k <= n1; k++)
{
int coefficient_index = coefficient_counter++;
float* ring_buffer_entry = stbir__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_pixel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_group + coefficient_index];
for (x = 0; x < output_w; x++)
{
int in_pixel_index = x * channels;
int c;
for (c = 0; c < channels; c++)
encode_buffer[in_pixel_index + c] += ring_buffer_entry[in_pixel_index + c] * coefficient;
}
}
break;
}
stbir__encode_scanline(stbir_info, output_w, (char *) output_data + output_row_start, encode_buffer, channels, alpha_channel, decode);
}