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Add missing padding pixel to avoid artifacts 

Using subpixel positioning we need one empty pixel as the left of each glyph.
This commit is contained in:
Francesco Abbate 2021-03-04 16:54:55 +01:00
parent 294f3f14fb
commit e441beae83
1 changed files with 13 additions and 5 deletions
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18
lib/font_renderer/font_renderer.cpp
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@ -233,13 +233,17 @@ FR_Bitmap *FR_Bake_Font_Bitmap(FR_Renderer *font_renderer, int font_height,
for (int i = 0; i < num_chars; i++) {
const agg::rect_i& gbounds = bounds[index[i]];
if (gbounds.x2 < gbounds.x1) continue;
if (x + gbounds.x2 + 1 >= pixels_width * subpixel_scale) {
// 1. It is very important to ensure that the x's increment below (1) and in
// (2), (3) and (4) are perfectly the same.
if (x + gbounds.x2 + 3 * subpixel_scale >= pixels_width * subpixel_scale) {
x = x_start;
y = y_bottom;
}
// 5. Ensure that y's increment below is exactly the same to the one used in (6)
const int glyph_y_bottom = y - 2 * pad_y - (gbounds.y2 - gbounds.y1);
y_bottom = (y_bottom > glyph_y_bottom ? glyph_y_bottom : y_bottom);
x = x + gbounds.x2 + 2 * subpixel_scale;
// 2. Ensure x's increment is aligned with (1)
x = x + gbounds.x2 + 3 * subpixel_scale;
}
const int pixels_height = -y_bottom + 1;
@ -262,13 +266,15 @@ FR_Bitmap *FR_Bake_Font_Bitmap(FR_Renderer *font_renderer, int font_height,
const agg::rect_i& gbounds = bounds[index[i]];
if (gbounds.x2 < gbounds.x1) continue;
if (x + gbounds.x2 + 1 >= pixels_width * subpixel_scale) {
// 3. Ensure x's increment is aligned with (1)
if (x + gbounds.x2 + 3 * subpixel_scale >= pixels_width * subpixel_scale) {
// No more space along x, begin writing the row below.
x = x_start;
y = y_bottom;
}
const int y_baseline = y - pad_y - gbounds.y2;
// 6. Ensure the y's increment below is aligned with the increment used in (5)
const int glyph_y_bottom = y - 2 * pad_y - (gbounds.y2 - gbounds.y1);
y_bottom = (y_bottom > glyph_y_bottom ? glyph_y_bottom : y_bottom);
@ -296,8 +302,10 @@ FR_Bitmap *FR_Bake_Font_Bitmap(FR_Renderer *font_renderer, int font_height,
}
glyph_trim_rect(ren_buf, glyph_info, subpixel_scale);
// When subpixel is activated we need one padding pixel on the left and on the right.
x = x + gbounds.x2 + 2 * subpixel_scale;
// When subpixel is activated we need one padding pixel on the left and on the right
// and one more because of subpixel positioning.
// 4. Ensure x's increment is aligned with (1)
x = x + gbounds.x2 + 3 * subpixel_scale;
}
delete [] index;
delete [] bounds;