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Add preliminary forward DCT

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This commit is contained in:
Pavel Krajcevski 2015-02-11 23:39:32 -08:00
parent a263907e0f
commit 4afacf384d
2 changed files with 77 additions and 0 deletions
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2
Base/include/FasTC/Image.h
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@ -130,6 +130,8 @@ namespace FasTC {
Image<IPixel> *channelOne,
Image<IPixel> *channelTwo,
Image<IPixel> *channelThree);
extern void DiscreteCosineXForm(Image<IPixel> *img, int blockSize);
} // namespace FasTC
#endif // __TEXCOMP_IMAGE_H__

75
Base/src/Image.cpp
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@ -610,4 +610,79 @@ void SplitChannels<Pixel>(const Image<Pixel> &in,
SplitChannelsImpl(in, channelOne, channelTwo, channelThree);
}
////////////////////////////////////////////////////////////////////////////////
//
// Discrete Cosine Transform
//
////////////////////////////////////////////////////////////////////////////////
static void DCT(Image<IPixel> *img) {
Image<IPixel> new_img = *img;
float N = static_cast<float>(img->GetWidth());
float M = static_cast<float>(img->GetHeight());
for (unsigned int v = 0; v < img->GetHeight(); ++v) {
for (unsigned int u = 0; u < img->GetWidth(); ++u) {
new_img(u, v) = 0.0f;
for (unsigned int y = 0; y < img->GetHeight(); ++y) {
for (unsigned int x = 0; x < img->GetWidth(); ++x) {
float fx = static_cast<float>(x);
float fy = static_cast<float>(y);
new_img(u, v) += (*img)(x, y)
* cos((2*fx + 1) / (2 * N))
* cos((2*fy + 1) / (2 * M));
}
}
if (u == 0 && v == 0) {
new_img(u, v) *= 0.5;
} else if (u == 0 || v == 0) {
new_img(u, v) /= sqrt(2);
}
new_img(u, v) *= 0.25;
}
}
*img = new_img;
}
extern void DiscreteCosineXForm(Image<IPixel> *img, int blockSize) {
Image<IPixel> block(blockSize, blockSize);
for (unsigned int j = 0; j < img->GetHeight(); j += blockSize) {
for (unsigned int i = 0; i < img->GetWidth(); i += blockSize) {
// Populate block
for (int y = 0; y < blockSize; ++y) {
for (int x = 0; x < blockSize; ++x) {
IPixel xx = std::min(img->GetWidth() - 1, i + x);
IPixel yy = std::min(img->GetHeight() - 1, j + y);
block(x, y) = (*img)(xx, yy);
}
}
// Transform it
DCT(&block);
// Put it back in the original image
for (int y = 0; y < blockSize; ++y) {
for (int x = 0; x < blockSize; ++x) {
if (i + x >= img->GetWidth()) {
continue;
}
if (j + y >= img->GetHeight()) {
continue;
}
assert (i + x <= img->GetWidth());
assert (j + y <= img->GetHeight());
(*img)(i + x, j + y) = block(x, y);
}
}
}
}
}
} // namespace FasTC