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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2020, Google Inc.
*
* thumbnailer.cpp - Simple image thumbnailer
*/
#include "thumbnailer.h"
#include <libcamera/formats.h>
#include "libcamera/internal/log.h"
using namespace libcamera;
LOG_DEFINE_CATEGORY(Thumbnailer)
Thumbnailer::Thumbnailer()
: valid_(false)
{
}
void Thumbnailer::configure(const Size &sourceSize, PixelFormat pixelFormat)
{
sourceSize_ = sourceSize;
pixelFormat_ = pixelFormat;
if (pixelFormat_ != formats::NV12) {
LOG(Thumbnailer, Error)
<< "Failed to configure: Pixel Format "
<< pixelFormat_.toString() << " unsupported.";
return;
}
targetSize_ = computeThumbnailSize();
valid_ = true;
}
/*
* The Exif specification recommends the width of the thumbnail to be a
* multiple of 16 (section 4.8.1). Hence, compute the corresponding height
* keeping the aspect ratio same as of the source.
*/
Size Thumbnailer::computeThumbnailSize() const
{
unsigned int targetHeight;
constexpr unsigned int kTargetWidth = 160;
targetHeight = kTargetWidth * sourceSize_.height / sourceSize_.width;
if (targetHeight & 1)
targetHeight++;
return Size(kTargetWidth, targetHeight);
}
void Thumbnailer::createThumbnail(const FrameBuffer &source,
std::vector<unsigned char> *destination)
{
MappedFrameBuffer frame(&source, PROT_READ);
if (!frame.isValid()) {
LOG(Thumbnailer, Error)
<< "Failed to map FrameBuffer : "
<< strerror(frame.error());
return;
}
if (!valid_) {
LOG(Thumbnailer, Error) << "Config is unconfigured or invalid.";
return;
}
const unsigned int sw = sourceSize_.width;
const unsigned int sh = sourceSize_.height;
const unsigned int tw = targetSize_.width;
const unsigned int th = targetSize_.height;
ASSERT(tw % 2 == 0 && th % 2 == 0);
/* Image scaling block implementing nearest-neighbour algorithm. */
unsigned char *src = static_cast<unsigned char *>(frame.maps()[0].data());
unsigned char *srcC = src + sh * sw;
unsigned char *srcCb, *srcCr;
unsigned char *dstY, *srcY;
size_t dstSize = (th * tw) + ((th / 2) * tw);
destination->resize(dstSize);
unsigned char *dst = destination->data();
unsigned char *dstC = dst + th * tw;
for (unsigned int y = 0; y < th; y += 2) {
unsigned int sourceY = (sh * y + th / 2) / th;
dstY = dst + y * tw;
srcY = src + sw * sourceY;
srcCb = srcC + (sourceY / 2) * sw + 0;
srcCr = srcC + (sourceY / 2) * sw + 1;
for (unsigned int x = 0; x < tw; x += 2) {
unsigned int sourceX = (sw * x + tw / 2) / tw;
dstY[x] = srcY[sourceX];
dstY[tw + x] = srcY[sw + sourceX];
dstY[x + 1] = srcY[sourceX + 1];
dstY[tw + x + 1] = srcY[sw + sourceX + 1];
dstC[(y / 2) * tw + x + 0] = srcCb[(sourceX / 2) * 2];
dstC[(y / 2) * tw + x + 1] = srcCr[(sourceX / 2) * 2];
}
}
}
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