nerdcruft/libcruft-util
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image: set the output values in downsample...

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Danny Robson 2015-02-04 18:39:40 +11:00
parent 52544605e5
commit 09be9f3cea
1 changed files with 8 additions and 7 deletions
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15
image.cpp
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@ -114,7 +114,9 @@ template <typename T>
util::image::buffer<T> util::image::buffer<T>
util::image::buffer<T>::downsample (unsigned factor) util::image::buffer<T>::downsample (unsigned factor)
{ {
CHECK_GT (factor, 1); CHECK_GE (factor, 1);
if (factor == 1)
return clone<T> ();
size_t w_ = w / factor; size_t w_ = w / factor;
size_t h_ = h / factor; size_t h_ = h / factor;
@ -128,13 +130,12 @@ util::image::buffer<T>::downsample (unsigned factor)
// Do a really shitty nearest neighbour average in src-space. // Do a really shitty nearest neighbour average in src-space.
for (size_t y = 0; y < out.h; ++y) for (size_t y = 0; y < out.h; ++y)
for (size_t x = 0; x < out.w; ++x) { for (size_t x = 0; x < out.w; ++x) {
size_t src00 = ((y * factor) + 0) * s + (x * factor) + 0; size_t src00 = (y + 0) * s * factor + (x * factor) + 0;
size_t src01 = ((y * factor) + 0) * s + (x * factor) + 1; size_t src01 = (y + 0) * s * factor + (x * factor) + 1;
size_t src10 = ((y * factor) + 1) * s + (x * factor) + 0; size_t src10 = (y + 1) * s * factor + (x * factor) + 0;
size_t src11 = ((y * factor) + 1) * s + (x * factor) + 1; size_t src11 = (y + 1) * s * factor + (x * factor) + 1;
size_t dst_offset = y * out.s + x; out.data[x + y * out.s] = (data[src00] + data[src01] + data[src10] + data[src11]) / 4;
out.data[dst_offset] = (src00 + src01 + src10 + src11) / 4;
} }
return out; return out;