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sw_engine: Improve image up-scaler quality

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Adjusted the sampling position basis by -0.5 pixel
to enhance edge line interpolation quality.

This change addresses an issue with the image up-scaling process,
resulting in clearer and more accurate visuals.

issue: https://github.com/thorvg/thorvg/issues/1949
This commit is contained in:
Hermet Park 2024-02-04 20:11:53 +09:00
parent ef5568fbd6
commit 2613521aa8
1 changed files with 10 additions and 10 deletions
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20
src/renderer/sw_engine/tvgSwRaster.cpp
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@ -257,15 +257,15 @@ static uint32_t _interpUpScaler(const uint32_t *img, TVG_UNUSED uint32_t stride,
auto ry2 = ry + 1;
if (ry2 >= h) ry2 = h - 1;
auto dx = static_cast<uint8_t>((sx - rx) * 255.0f);
auto dy = static_cast<uint8_t>((sy - ry) * 255.0f);
auto dx = (sx > 0.0f) ? static_cast<uint8_t>((sx - rx) * 255.0f) : 0;
auto dy = (sy > 0.0f) ? static_cast<uint8_t>((sy - ry) * 255.0f) : 0;
auto c1 = img[rx + ry * w];
auto c2 = img[rx2 + ry * w];
auto c3 = img[rx2 + ry2 * w];
auto c4 = img[rx + ry2 * w];
auto c3 = img[rx + ry2 * w];
auto c4 = img[rx2 + ry2 * w];
return INTERPOLATE(INTERPOLATE(c3, c4, dx), INTERPOLATE(c2, c1, dx), dy);
return INTERPOLATE(INTERPOLATE(c4, c3, dx), INTERPOLATE(c2, c1, dx), dy);
}
@ -671,10 +671,10 @@ static bool _rasterRle(SwSurface* surface, SwRleData* rle, uint8_t r, uint8_t g,
/************************************************************************/
#define SCALED_IMAGE_RANGE_Y(y) \
auto sy = (y) * itransform->e22 + itransform->e23; \
auto my = (int32_t)round(sy); \
if (my < 0 || (uint32_t)sy >= image->h) continue; \
auto sy = (y) * itransform->e22 + itransform->e23 - 0.49f; \
if (sy <= -0.5f || (uint32_t)(sy + 0.5f) >= image->h) continue; \
if (scaleMethod == _interpDownScaler) { \
auto my = (int32_t)round(sy); \
miny = my - (int32_t)sampleSize; \
if (miny < 0) miny = 0; \
maxy = my + (int32_t)sampleSize; \
@ -682,8 +682,8 @@ static bool _rasterRle(SwSurface* surface, SwRleData* rle, uint8_t r, uint8_t g,
}
#define SCALED_IMAGE_RANGE_X \
auto sx = x * itransform->e11 + itransform->e13; \
if ((int32_t)round(sx) < 0 || (uint32_t) sx >= image->w) continue;
auto sx = (x) * itransform->e11 + itransform->e13 - 0.49f; \
if (sx <= -0.5f || (uint32_t)(sx + 0.5f) >= image->w) continue; \
#if 0 //Enable it when GRAYSCALE image is supported