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graphics: Adjust texel values that can be exactly on the edges of the source rect (#491)

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This commit is contained in:
Hajime Hoshi 2018-02-03 02:07:46 +09:00
parent b9c115eb92
commit beaa060ce3
2 changed files with 20 additions and 4 deletions
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15
internal/graphics/shader.go
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@ -51,12 +51,19 @@ varying vec2 varying_tex_coord;
varying vec2 varying_tex_coord_min;
varying vec2 varying_tex_coord_max;
const float minHighpValue = 1.0 / 32768.0;
void main(void) {
varying_tex_coord = vec2(tex_coord[0], tex_coord[1]);
varying_tex_coord_min =
vec2(min(tex_coord[0], tex_coord[2]), min(tex_coord[1], tex_coord[3]));
varying_tex_coord_max =
vec2(max(tex_coord[0], tex_coord[2]), max(tex_coord[1], tex_coord[3]));
// varying_tex_coord_min and varying_tex_coord_max mean endmost texel values
// in the source rect. As varying_tex_coord is adjusted with minHighpValue
// in vertices.go, re-adjust them so that exact endmost texel values.
varying_tex_coord_min = vec2(
min(tex_coord[0], tex_coord[2]) - minHighpValue,
min(tex_coord[1], tex_coord[3]) - minHighpValue);
varying_tex_coord_max = vec2(
max(tex_coord[0], tex_coord[2]) + minHighpValue,
max(tex_coord[1], tex_coord[3]) + minHighpValue);
gl_Position = projection_matrix * vec4(vertex, 0, 1);
}
`

9
vertices.go
View File

@ -87,6 +87,15 @@ func vertices(sx0, sy0, sx1, sy1 int, width, height int, geo *affine.GeoM) []flo
hf := float32(h)
u0, v0, u1, v1 := float32(sx0)/wf, float32(sy0)/hf, float32(sx1)/wf, float32(sy1)/hf
// Adjust texels to be slightly inside the source rect. Without this
// adjustment, texels can be exactly as same values as the edges'
// positions and it could happen that nothing is rendered. (#491)
const minHighpValue = 1.0/32768.0
u0 += minHighpValue
v0 += minHighpValue
u1 -= minHighpValue
v1 -= minHighpValue
x, y := geo.Apply32(x0, y0)
// Vertex coordinates
vs[0] = x