QTransform
ImageTransformation::calcPostScaleXform(Dpi const& target_dpi)
{
if (target_dpi.isNull()) {
return QTransform();
}
// We are going to measure the effective DPI after the previous transforms.
// Normally m_preScaledDpi would be symmetric, so we could just
// use that, but just in case ...
QTransform const to_orig(m_postScaleXform * m_transform.inverted());
// IMPORTANT: in the above line we assume post-scale is the last transform.
QLineF const hor_unit(QPointF(0, 0), QPointF(1, 0));
QLineF const vert_unit(QPointF(0, 0), QPointF(0, 1));
QLineF const orig_hor_unit(to_orig.map(hor_unit));
QLineF const orig_vert_unit(to_orig.map(vert_unit));
double const xscale = target_dpi.horizontal() * orig_hor_unit.length() / m_origDpi.horizontal();
double const yscale = target_dpi.vertical() * orig_vert_unit.length() / m_origDpi.vertical();
QTransform xform;
xform.scale(xscale, yscale);
return xform;
}
void
FixDpiDialog::setDpiForm(ImageMetadata const& metadata)
{
Dpi const dpi(metadata.dpi());
if (dpi.isNull()) {
resetDpiForm();
return;
}
m_xDpiInitialValue = QString::number(dpi.horizontal());
m_yDpiInitialValue = QString::number(dpi.vertical());
m_selectedItemPixelSize = metadata.size();
xDpi->setText(m_xDpiInitialValue);
yDpi->setText(m_yDpiInitialValue);
dpiValueChanged();
}
void
ImageTransformation::preScaleToDpi(Dpi const& dpi)
{
if (m_origDpi.isNull() || dpi.isNull()) {
return;
}
m_preScaledDpi = dpi;
double const xscale = (double)dpi.horizontal() / m_origDpi.horizontal();
double const yscale = (double)dpi.vertical() / m_origDpi.vertical();
QSizeF const new_pre_scaled_image_size(
m_origRect.width() * xscale, m_origRect.height() * yscale
);
// Undo's for the specified steps.
QTransform const undo21(m_preRotateXform.inverted() * m_preScaleXform.inverted());
QTransform const undo4321(m_postRotateXform.inverted() * m_preCropXform.inverted() * undo21);
// Update transform #1: pre-scale.
m_preScaleXform.reset();
m_preScaleXform.scale(xscale, yscale);
// Update transform #2: pre-rotate.
m_preRotateXform = m_preRotation.transform(new_pre_scaled_image_size);
// Update transform #3: pre-crop.
QTransform const redo12(m_preScaleXform * m_preRotateXform);
m_preCropArea = (undo21 * redo12).map(m_preCropArea);
m_preCropXform = calcCropXform(m_preCropArea);
// Update transform #4: post-rotate.
m_postRotateXform = calcPostRotateXform(m_postRotation);
// Update transform #5: post-crop.
QTransform const redo1234(redo12 * m_preCropXform * m_postRotateXform);
m_postCropArea = (undo4321 * redo1234).map(m_postCropArea);
m_postCropXform = calcCropXform(m_postCropArea);
// Update transform #6: post-scale.
m_postScaleXform = calcPostScaleXform(m_postScaledDpi);
update();
}
void
ImageTransformation::preScaleToDpi(Dpi const& dpi)
{
if (m_origDpi.isNull() || dpi.isNull()) {
return;
}
m_preScaledDpi = dpi;
double const xscale = (double)dpi.horizontal() / m_origDpi.horizontal();
double const yscale = (double)dpi.vertical() / m_origDpi.vertical();
QSizeF const new_pre_scaled_image_size(
m_origRect.width() * xscale, m_origRect.height() * yscale
);
// Reverse pre-rotation.
QPolygonF tmp_crop_area(m_preRotateXform.inverted().map(m_cropArea));
// Reverse pre-scaling.
tmp_crop_area = m_preScaleXform.inverted().map(tmp_crop_area);
// Update m_preScaleXform and m_preRotateXform.
m_preScaleXform.reset();
m_preScaleXform.scale(xscale, yscale);
m_preRotateXform = m_preRotation.transform(new_pre_scaled_image_size);
// Apply new pre-scaling.
tmp_crop_area = m_preScaleXform.map(tmp_crop_area);
// Re-apply pre-rotation.
m_cropArea = m_preRotateXform.map(tmp_crop_area);
m_cropXform = calcCropXform(m_cropArea);
m_postRotateXform = calcPostRotateXform(m_postRotation);
update();
}
GrayImage
TextLineTracer::downscale(GrayImage const& input, Dpi const& dpi)
{
// Downscale to 200 DPI.
QSize downscaled_size(input.size());
if (dpi.horizontal() < 180 || dpi.horizontal() > 220 || dpi.vertical() < 180 || dpi.vertical() > 220) {
downscaled_size.setWidth(std::max<int>(1, input.width() * 200 / dpi.horizontal()));
downscaled_size.setHeight(std::max<int>(1, input.height() * 200 / dpi.vertical()));
}
return scaleToGray(input, downscaled_size);
}
