Merge pull request #810 from arummler/feature-graphics-primitives-squashed-additional-commits

Image speed improvement and additional transparency feature

sources/qetgraphicsitem/diagramimageitem.cpp

@@ -1064,23 +1064,24 @@ QVariant DiagramImageItem::itemChange(GraphicsItemChange change, const QVariant
 	@brief DiagramImageItem::computeDisplayPixmap
 	Re-derives what pixmap_ should be from first principles: crop the
 	true original down to the chosen region, then colour-key whichever
-	colours have been picked out of it. Used whenever crop() or
-	setTransparentColor() changes one of those two independently, so
-	the other's effect is correctly re-applied on top rather than lost
-	or compounded -- cropping after colours were already picked has to
-	still show them keyed out; picking colours after a crop has to only
-	ever consider what's still actually part of the image.
+	colours have been picked out of it, each at its own tolerance. Used
+	whenever crop() or setTransparentColor() changes one of those two
+	independently, so the other's effect is correctly re-applied on top
+	rather than lost or compounded -- cropping after colours were
+	already picked has to still show them keyed out; picking colours
+	after a crop has to only ever consider what's still actually part
+	of the image.
 	@param base the true, uncropped original
 	@param cropRect the region of base to keep, in base's own coordinates
-	@param colors colours to key transparent within the cropped region
-	@param tolerance how loosely to match those colours, 0-100
+	@param colors colours (each with its own tolerance) to key transparent within the cropped region
 */
-QPixmap DiagramImageItem::computeDisplayPixmap(const QPixmap &base, const QRect &cropRect, const QList<QColor> &colors, int tolerance)
+QPixmap DiagramImageItem::computeDisplayPixmap(const QPixmap &base, const QRect &cropRect,
+		const QList<ImageTransparentColorDialog::PickedColor> &colors)
 {
 	const QPixmap cropped = cropRect == base.rect() ? base : base.copy(cropRect);
 	if (colors.isEmpty())
 		return cropped;
-	return QPixmap::fromImage(ImageTransparentColorDialog::applyColorKey(cropped.toImage(), colors, tolerance));
+	return QPixmap::fromImage(ImageTransparentColorDialog::applyColorKey(cropped.toImage(), colors));
 }
 
 /**
@@ -1142,19 +1143,25 @@ bool DiagramImageItem::fromXml(const QDomElement &e)
 	m_base_pixmap = pixmap;
 	m_crop_rect = pixmap.rect();
 	m_transparent_colors.clear();
-	m_transparent_tolerance = 10;
 
 	const QDomElement colorsElement = e.firstChildElement("transparent_colors");
 	bool hasColors = !colorsElement.isNull();
 	if (hasColors)
 	{
-		m_transparent_tolerance = colorsElement.attribute("tolerance", "10").toInt();
+		// Files saved before per-colour tolerance existed wrote a
+		// single value on the wrapper element itself, shared by every
+		// colour -- kept here purely as the fallback default for a
+		// <color> that doesn't carry its own attribute, which for
+		// those old files is every one of them, exactly reproducing
+		// what they used to do (one tolerance applied to all of them).
+		const int wrapperTolerance = colorsElement.attribute("tolerance", "10").toInt();
 		for (const QDomElement &colorElement : QET::findInDomElement(colorsElement, "color"))
 		{
-			m_transparent_colors.append(QColor(
-					colorElement.attribute("r").toInt(),
-					colorElement.attribute("g").toInt(),
-					colorElement.attribute("b").toInt()));
+			m_transparent_colors.append({
+					QColor(colorElement.attribute("r").toInt(),
+					       colorElement.attribute("g").toInt(),
+					       colorElement.attribute("b").toInt()),
+					colorElement.attribute("tolerance", QString::number(wrapperTolerance)).toInt()});
 		}
 	}
 
@@ -1296,13 +1303,21 @@ QDomElement DiagramImageItem::toXml(QDomDocument &document) const
 	if (hasColors)
 	{
 		QDomElement colorsElement = document.createElement("transparent_colors");
-		colorsElement.setAttribute("tolerance", m_transparent_tolerance);
-		for (const QColor &color : m_transparent_colors)
+		// Best-effort fallback for an OLDER version of this same code
+		// (from before per-colour tolerance existed) reading a file
+		// saved by this one: uses the first colour's own tolerance as
+		// a single, plausible value rather than some fixed default,
+		// in case it ever needs to open a file like this. Newer code
+		// (including this version) always prefers each <color>'s own
+		// attribute below over this one.
+		colorsElement.setAttribute("tolerance", m_transparent_colors.first().tolerance);
+		for (const auto &pc : m_transparent_colors)
 		{
 			QDomElement colorElement = document.createElement("color");
-			colorElement.setAttribute("r", color.red());
-			colorElement.setAttribute("g", color.green());
-			colorElement.setAttribute("b", color.blue());
+			colorElement.setAttribute("r", pc.color.red());
+			colorElement.setAttribute("g", pc.color.green());
+			colorElement.setAttribute("b", pc.color.blue());
+			colorElement.setAttribute("tolerance", pc.tolerance);
 			colorsElement.appendChild(colorElement);
 		}
 		result.appendChild(colorsElement);
@@ -1520,12 +1535,11 @@ void DiagramImageItem::setTransparentColor()
 
 	QWidget *parentWidget = diagram()->views().isEmpty() ? nullptr : diagram()->views().first();
 	const QPixmap croppedBase = m_base_pixmap.copy(m_crop_rect);
-	ImageTransparentColorDialog dialog(croppedBase, m_transparent_colors, m_transparent_tolerance, parentWidget);
+	ImageTransparentColorDialog dialog(croppedBase, m_transparent_colors, parentWidget);
 	if (dialog.exec() != QDialog::Accepted)
 		return;
 
 	m_transparent_colors = dialog.pickedColors();
-	m_transparent_tolerance = dialog.tolerance();
 
 	const QPixmap oldPixmap = pixmap_;
 	const QPixmap newPixmap = dialog.resultPixmap();
@@ -1609,7 +1623,7 @@ void DiagramImageItem::crop()
 	const QPointF oldPos = pos();
 
 	const QPixmap oldPixmap = pixmap_;
-	const QPixmap newPixmap = computeDisplayPixmap(m_base_pixmap, newCropRect, m_transparent_colors, m_transparent_tolerance);
+	const QPixmap newPixmap = computeDisplayPixmap(m_base_pixmap, newCropRect, m_transparent_colors);
 	m_crop_rect = newCropRect;
 
 	// boundingRect() is exactly QRectF(pixmap_.rect()) (confirmed by

sources/qetgraphicsitem/diagramimageitem.h

@@ -20,6 +20,7 @@
 
 #include "qetgraphicsitem.h"
 #include "shapetransform.h"
+#include "../ui/imagetransparentcolordialog.h"
 
 #include <QColor>
 #include <QList>
@@ -128,7 +129,7 @@ class DiagramImageItem : public QetGraphicsItem {
 	void setTransparentColor();
 	void crop();
 	void restoreAspectRatio();
-	static QPixmap computeDisplayPixmap(const QPixmap &base, const QRect &cropRect, const QList<QColor> &colors, int tolerance);
+	static QPixmap computeDisplayPixmap(const QPixmap &base, const QRect &cropRect, const QList<ImageTransparentColorDialog::PickedColor> &colors);
 
 	void toggleHandleMode();
 	HandleMode nextHandleMode() const;
@@ -161,22 +162,22 @@ class DiagramImageItem : public QetGraphicsItem {
 	QPixmap pixmap_;
 	// The true, pristine original -- never itself cropped or colour-
 	// keyed. pixmap_ (the displayed result) is always re-derived from
-	// this plus m_crop_rect and m_transparent_colors/tolerance, via
-	// computeDisplayPixmap(). Without keeping this separate, re-opening
-	// either the crop or transparency dialog after using the other
-	// would show an already-modified image as if it were the source --
-	// areas already cropped away or coloured out would be gone for
-	// good, with no way to recover or adjust them, only start over.
-	// Updated by whatever genuinely replaces or reorients the image's
-	// actual content (construction, replaceImage(), and mirror(), which
-	// also mirrors m_crop_rect to keep referring to the same region of
-	// the now-flipped base) -- never by crop() or setTransparentColor()
+	// this plus m_crop_rect and m_transparent_colors (each colour
+	// carrying its own tolerance), via computeDisplayPixmap(). Without
+	// keeping this separate, re-opening either the crop or
+	// transparency dialog after using the other would show an
+	// already-modified image as if it were the source -- areas already
+	// cropped away or coloured out would be gone for good, with no way
+	// to recover or adjust them, only start over. Updated by whatever
+	// genuinely replaces or reorients the image's actual content
+	// (construction, replaceImage(), and mirror(), which also mirrors
+	// m_crop_rect to keep referring to the same region of the
+	// now-flipped base) -- never by crop() or setTransparentColor()
 	// themselves, which only ever change which subset of this base is
 	// shown.
 	QPixmap m_base_pixmap;
 	QRect m_crop_rect;   // relative to m_base_pixmap; equals m_base_pixmap.rect() when nothing has been cropped
-	QList<QColor> m_transparent_colors;
-	int m_transparent_tolerance = 10;
+	QList<ImageTransparentColorDialog::PickedColor> m_transparent_colors;
 
 	// Independent scaleX/scaleY here is the actual point of this whole
 	// member: QGraphicsItem::scale() is a single, uniform float, which

sources/ui/imagetransparentcolordialog.cpp

@@ -25,6 +25,7 @@
 #include <QPainter>
 #include <QPushButton>
 #include <QSlider>
+#include <QToolButton>
 #include <QVBoxLayout>
 #include <QVector>
 
@@ -48,10 +49,10 @@ ClickableImageLabel::ClickableImageLabel(const QImage &sourceImage, QWidget *par
 	const qreal scaleH = qreal(MAX_DISPLAY_SIZE) / m_source.height();
 	m_displayScale = qMin(qreal(1.0), qMin(scaleW, scaleH));   // never upscale a small image, only ever shrink a large one
 
-	const QImage displayImage = (m_displayScale < 1.0)
+	m_displayImage = (m_displayScale < 1.0)
 			? m_source.scaled(m_source.size() * m_displayScale, Qt::KeepAspectRatio, Qt::SmoothTransformation)
 			: m_source;
-	setPixmap(QPixmap::fromImage(displayImage));
+	setPixmap(QPixmap::fromImage(m_displayImage));
 	setCursor(Qt::CrossCursor);
 	setToolTip(tr("Cliquez pour choisir une couleur"));
 }
@@ -91,23 +92,23 @@ void ClickableImageLabel::mousePressEvent(QMouseEvent *event)
 	@param pixmap the image to pick a transparent colour from
 	@param parent
 */
-ImageTransparentColorDialog::ImageTransparentColorDialog(const QPixmap &basePixmap, const QList<QColor> &existingColors,
-		int existingTolerance, QWidget *parent) :
+ImageTransparentColorDialog::ImageTransparentColorDialog(const QPixmap &basePixmap,
+		const QList<PickedColor> &existingColors, QWidget *parent) :
 	QDialog(parent),
 	m_sourceImage(basePixmap.toImage()),
-	m_pickedColors(existingColors),
-	m_tolerance(existingTolerance)
+	m_pickedColors(existingColors)
 {
 	setWindowTitle(tr("Couleur transparente"));
 
+	if (!m_pickedColors.isEmpty())
+		m_lastToleranceUsed = m_pickedColors.last().tolerance;
+
 	m_sourceLabel = new ClickableImageLabel(m_sourceImage, this);
+	m_previewSourceImage = m_sourceLabel->displayImage();
 	m_previewLabel = new QLabel(this);
 
 	m_hintLabel = new QLabel(this);
-
-	m_toleranceSlider = new QSlider(Qt::Horizontal, this);
-	m_toleranceSlider->setRange(0, 100);
-	m_toleranceSlider->setValue(m_tolerance);
+	m_hintLabel->setWordWrap(true);
 
 	auto *buttons = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel, this);
 	m_okButton = buttons->button(QDialogButtonBox::Ok);
@@ -119,29 +120,19 @@ ImageTransparentColorDialog::ImageTransparentColorDialog(const QPixmap &basePixm
 	grid->addWidget(m_sourceLabel, 1, 0);
 	grid->addWidget(m_previewLabel, 1, 1);
 
-	// An empty row to start with if existingColors is empty --
-	// rebuildSwatches() below populates it either way (including from
-	// existingColors on the first call), and again as colours get
-	// added or removed.
-	m_swatchesLayout = new QHBoxLayout;
-
-	auto *colorRow = new QHBoxLayout;
-	colorRow->addWidget(m_hintLabel);
-	colorRow->addStretch();
-	colorRow->addLayout(m_swatchesLayout);
-
-	auto *toleranceRow = new QHBoxLayout;
-	toleranceRow->addWidget(new QLabel(tr("Tolérance")));
-	toleranceRow->addWidget(m_toleranceSlider);
+	// One row per picked colour, appended/removed as rebuildSwatches()
+	// runs -- starts empty either way, populated by the very first
+	// rebuildSwatches() call below (including from existingColors, if
+	// any were passed in).
+	m_swatchesLayout = new QVBoxLayout;
 
 	auto *mainLayout = new QVBoxLayout(this);
 	mainLayout->addLayout(grid);
-	mainLayout->addLayout(colorRow);
-	mainLayout->addLayout(toleranceRow);
+	mainLayout->addWidget(m_hintLabel);
+	mainLayout->addLayout(m_swatchesLayout);
 	mainLayout->addWidget(buttons);
 
 	connect(m_sourceLabel, &ClickableImageLabel::colorPicked, this, &ImageTransparentColorDialog::onColorPicked);
-	connect(m_toleranceSlider, &QSlider::valueChanged, this, &ImageTransparentColorDialog::onToleranceChanged);
 	connect(buttons, &QDialogButtonBox::accepted, this, &QDialog::accept);
 	connect(buttons, &QDialogButtonBox::rejected, this, &QDialog::reject);
 
@@ -156,30 +147,55 @@ ImageTransparentColorDialog::ImageTransparentColorDialog(const QPixmap &basePixm
 	the first choice, with no way to work with more than one colour (a
 	white background *and* a grey border, say) in the same pass.
 	Skips an exact duplicate rather than adding a second, indistinguishable
-	swatch for it.
+	row for it. The new colour is seeded with whatever tolerance was
+	last used (not some fixed default), so successive picks in one
+	session feel consistent.
 	@param color the colour sampled from the source image
 */
 void ImageTransparentColorDialog::onColorPicked(const QColor &color)
 {
-	if (m_pickedColors.contains(color))
-		return;
+	for (const PickedColor &existing : std::as_const(m_pickedColors))
+		if (existing.color == color)
+			return;
 
-	m_pickedColors.append(color);
+	m_pickedColors.append({color, m_lastToleranceUsed});
 	m_okButton->setEnabled(true);
 	rebuildSwatches();
 	updatePreview();
 }
 
+/**
+	@brief ImageTransparentColorDialog::setToleranceForIndex
+	Updates one colour's own tolerance in place -- deliberately doesn't
+	call rebuildSwatches(): only a number changed, not which rows exist
+	or what order they're in, so recreating every row's widgets (and,
+	worse, the very slider currently being dragged) on each tick would
+	be both wasteful and liable to interrupt the drag itself.
+	@param index which entry in m_pickedColors changed
+	@param value its new tolerance, 0-100
+*/
+void ImageTransparentColorDialog::setToleranceForIndex(int index, int value)
+{
+	if (index < 0 || index >= m_pickedColors.size())
+		return;
+	m_pickedColors[index].tolerance = value;
+	m_lastToleranceUsed = value;
+	updatePreview();
+}
+
 /**
 	@brief ImageTransparentColorDialog::removeColor
 	Removes one colour from the set -- the counterpart onColorPicked()
 	was missing entirely before: picking the wrong pixel by mistake had
 	no way to undo except cancelling the whole dialog and starting over.
-	@param color the colour to remove
+	@param index position in m_pickedColors to remove
 */
-void ImageTransparentColorDialog::removeColor(const QColor &color)
+void ImageTransparentColorDialog::removeColor(int index)
 {
-	m_pickedColors.removeAll(color);
+	if (index < 0 || index >= m_pickedColors.size())
+		return;
+
+	m_pickedColors.removeAt(index);
 	m_okButton->setEnabled(!m_pickedColors.isEmpty());
 	rebuildSwatches();
 	updatePreview();
@@ -187,11 +203,16 @@ void ImageTransparentColorDialog::removeColor(const QColor &color)
 
 /**
 	@brief ImageTransparentColorDialog::rebuildSwatches
-	Rebuilds the row of picked-colour swatches from scratch against the
+	Rebuilds the list of picked-colour rows from scratch against the
 	current m_pickedColors -- simpler and safer than trying to
-	incrementally add/remove individual widgets in sync with the list,
+	incrementally add/remove individual rows in sync with the list,
 	given the list only ever changes one colour at a time and is never
-	large enough for a full rebuild to be a real cost.
+	large enough for a full rebuild to be a real cost. Each row is a
+	colour swatch (a plain, round, non-interactive indicator -- there's
+	nothing left to click it FOR, now that each row carries its own
+	slider instead of one shared slider needing a row selected first),
+	that row's own tolerance slider, and a small "x" button that
+	removes it.
 */
 void ImageTransparentColorDialog::rebuildSwatches()
 {
@@ -202,88 +223,109 @@ void ImageTransparentColorDialog::rebuildSwatches()
 		delete item;
 	}
 
-	for (const QColor &color : std::as_const(m_pickedColors))
+	for (int i = 0; i < m_pickedColors.size(); ++i)
 	{
-		auto *swatch = new QPushButton(this);
+		const PickedColor &pc = m_pickedColors.at(i);
+
+		auto *row = new QWidget(this);
+		auto *rowLayout = new QHBoxLayout(row);
+		rowLayout->setContentsMargins(0, 0, 0, 0);
+
+		auto *swatch = new QLabel(row);
 		swatch->setFixedSize(24, 24);
-		swatch->setStyleSheet(QStringLiteral("background-color: rgb(%1,%2,%3); border: 1px solid palette(mid);")
-				.arg(color.red()).arg(color.green()).arg(color.blue()));
-		swatch->setToolTip(tr("rgb(%1, %2, %3) -- cliquer pour retirer").arg(color.red()).arg(color.green()).arg(color.blue()));
-		connect(swatch, &QPushButton::clicked, this, [this, color]() { removeColor(color); });
-		m_swatchesLayout->addWidget(swatch);
+		swatch->setStyleSheet(QStringLiteral(
+				"background-color: rgb(%1,%2,%3); border: 1px solid palette(mid); border-radius: 12px;")
+				.arg(pc.color.red()).arg(pc.color.green()).arg(pc.color.blue()));
+		swatch->setToolTip(tr("rgb(%1, %2, %3)").arg(pc.color.red()).arg(pc.color.green()).arg(pc.color.blue()));
+
+		auto *slider = new QSlider(Qt::Horizontal, row);
+		slider->setRange(0, 100);
+		slider->setValue(pc.tolerance);
+		slider->setToolTip(tr("Tolérance pour cette couleur"));
+		connect(slider, &QSlider::valueChanged, this, [this, i](int value) { setToleranceForIndex(i, value); });
+
+		auto *removeButton = new QToolButton(row);
+		removeButton->setText(QStringLiteral("×"));
+		removeButton->setToolTip(tr("Retirer cette couleur"));
+		connect(removeButton, &QToolButton::clicked, this, [this, i]() { removeColor(i); });
+
+		rowLayout->addWidget(swatch);
+		rowLayout->addWidget(slider);
+		rowLayout->addWidget(removeButton);
+		m_swatchesLayout->addWidget(row);
 	}
 
 	m_hintLabel->setText(m_pickedColors.isEmpty()
 			? tr("Cliquez sur l'image pour choisir une couleur")
-			: tr("Cliquez sur l'image pour ajouter une couleur, ou sur une pastille pour la retirer"));
-}
-
-/**
-	@brief ImageTransparentColorDialog::onToleranceChanged
-	@param value the new tolerance, 0-100
-*/
-void ImageTransparentColorDialog::onToleranceChanged(int value)
-{
-	m_tolerance = value;
-	if (!m_pickedColors.isEmpty())
-		updatePreview();
+			: tr("Cliquez sur l'image pour ajouter une couleur. Ajustez la tolérance de chaque couleur avec son curseur, ou cliquez sur × pour la retirer."));
 }
 
 /**
 	@brief ImageTransparentColorDialog::updatePreview
 	Recomputes the checkerboard-backed preview against the current set
-	of picked colours and the shared tolerance. Always runs against
-	m_sourceImage (the original, full-resolution image), not any
-	already-keyed result -- so adjusting the tolerance, or adding or
-	removing a colour, re-evaluates every picked colour from scratch
-	each time rather than compounding successive passes.
+	of picked colours, each at its own tolerance. Runs against
+	m_previewSourceImage (the same downsampled copy ClickableImageLabel
+	already computed for its own display, not the full-resolution
+	m_sourceImage) -- this fires on every tolerance slider tick, not
+	just on release, and a full-resolution O(width*height*colours) pass
+	per tick was visibly laggy on a large source image. resultPixmap(),
+	below, still computes the final, committed result at full
+	resolution -- only this live preview is downsampled. Always
+	re-evaluates every picked colour from scratch against
+	m_previewSourceImage, not any already-keyed result, so adjusting a
+	tolerance or adding/removing a colour never compounds successive
+	passes.
 */
 void ImageTransparentColorDialog::updatePreview()
 {
-	const QImage keyed = applyColorKey(m_sourceImage, m_pickedColors, m_tolerance);
+	const QImage keyed = applyColorKey(m_previewSourceImage, m_pickedColors);
 	m_previewLabel->setPixmap(onCheckerboard(keyed));
 }
 
 /**
 	@brief ImageTransparentColorDialog::resultPixmap
-	@return the colour-keyed pixmap against every picked colour, or the
-	original pixmap unchanged if none were ever picked (the Ok button
-	stays disabled until at least one is, so this is mostly a defensive
-	fallback).
+	@return the colour-keyed pixmap against every picked colour, each at
+	its own tolerance, or the original pixmap unchanged if none were
+	ever picked (the Ok button stays disabled until at least one is, so
+	this is mostly a defensive fallback).
 */
 QPixmap ImageTransparentColorDialog::resultPixmap() const
 {
 	if (m_pickedColors.isEmpty())
 		return QPixmap::fromImage(m_sourceImage);
-	return QPixmap::fromImage(applyColorKey(m_sourceImage, m_pickedColors, m_tolerance));
+	return QPixmap::fromImage(applyColorKey(m_sourceImage, m_pickedColors));
 }
 
 /**
 	@brief ImageTransparentColorDialog::applyColorKey
 	Binary transparency within tolerance, not a smooth falloff: every
-	pixel within `tolerance` (0-100, mapped onto the maximum possible
-	RGB distance) of *any* of keyColors becomes fully transparent,
-	everything else keeps its existing alpha untouched. Squared distance
-	throughout, avoiding a sqrt per pixel; breaks out of the inner loop
-	on the first matching colour, since further matches wouldn't change
-	the outcome.
+	pixel within a colour's own `tolerance` (0-100, mapped onto the
+	maximum possible RGB distance) of that colour becomes fully
+	transparent, everything else keeps its existing alpha untouched --
+	each of keyColors is checked against its own threshold, not one
+	shared across all of them, since a background colour and a border
+	colour rarely call for the same looseness of match. Squared
+	distance throughout, avoiding a sqrt per pixel; breaks out of the
+	inner loop on the first matching colour, since further matches
+	wouldn't change the outcome.
 	@param source the image to key
-	@param keyColors the colours to make transparent
-	@param tolerance 0 (exact match only) to 100 (everything)
+	@param keyColors the colours (each with its own tolerance) to make transparent
 	@return the resulting image, always in Format_ARGB32
 */
-QImage ImageTransparentColorDialog::applyColorKey(const QImage &source, const QList<QColor> &keyColors, int tolerance)
+QImage ImageTransparentColorDialog::applyColorKey(const QImage &source, const QList<PickedColor> &keyColors)
 {
 	QImage result = source.convertToFormat(QImage::Format_ARGB32);
 	if (keyColors.isEmpty())
 		return result;
 
-	QVector<QRgb> keys;
+	struct KeyEntry { QRgb rgb; qint64 threshold; };
+	QVector<KeyEntry> keys;
 	keys.reserve(keyColors.size());
-	for (const QColor &c : keyColors)
-		keys.append(c.rgb());
-
-	const qint64 threshold = qint64(tolerance) * tolerance * 3 * 255 * 255 / (100 * 100);
+	for (const PickedColor &pc : keyColors)
+	{
+		const qint64 threshold = qint64(pc.tolerance) * pc.tolerance * 3 * 255 * 255 / (100 * 100);
+		keys.append({pc.color.rgb(), threshold});
+	}
 
 	for (int y = 0; y < result.height(); ++y)
 	{
@@ -291,11 +333,11 @@ QImage ImageTransparentColorDialog::applyColorKey(const QImage &source, const QL
 		for (int x = 0; x < result.width(); ++x)
 		{
 			const QRgb px = line[x];
-			for (const QRgb &key : keys)
+			for (const KeyEntry &key : std::as_const(keys))
 			{
-				const int dr = qRed(px) - qRed(key), dg = qGreen(px) - qGreen(key), db = qBlue(px) - qBlue(key);
+				const int dr = qRed(px) - qRed(key.rgb), dg = qGreen(px) - qGreen(key.rgb), db = qBlue(px) - qBlue(key.rgb);
 				const qint64 distSq = qint64(dr) * dr + qint64(dg) * dg + qint64(db) * db;
-				if (distSq <= threshold)
+				if (distSq <= key.threshold)
 				{
 					line[x] = qRgba(qRed(px), qGreen(px), qBlue(px), 0);
 					break;

sources/ui/imagetransparentcolordialog.h

@@ -24,9 +24,8 @@
 #include <QLabel>
 #include <QList>
 
-class QSlider;
+class QVBoxLayout;
 class QPushButton;
-class QHBoxLayout;
 class QMouseEvent;
 
 /**
@@ -45,6 +44,17 @@ class ClickableImageLabel : public QLabel
 	public:
 		explicit ClickableImageLabel(const QImage &sourceImage, QWidget *parent = nullptr);
 
+		/// The same downsampled image already computed for display --
+		/// reused as the live-preview source so a tolerance drag runs
+		/// its per-tick colour-key pass against a small image instead
+		/// of the full-resolution one, which on a large source (a
+		/// scanned schematic background, several Mpx) made every
+		/// intermediate slider tick visibly lag. resultPixmap() still
+		/// computes the final, committed result from the true
+		/// full-resolution source -- only the live preview is
+		/// downsampled.
+		QImage displayImage() const { return m_displayImage; }
+
 	signals:
 		void colorPicked(const QColor &color);
 
@@ -53,6 +63,7 @@ class ClickableImageLabel : public QLabel
 
 	private:
 		QImage m_source;
+		QImage m_displayImage;
 		qreal m_displayScale = 1.0;
 };
 
@@ -60,73 +71,88 @@ class ClickableImageLabel : public QLabel
 	@brief The ImageTransparentColorDialog class
 	Lets the user click directly on a preview of the image to sample one
 	or more colors -- each click adds to the set rather than replacing
-	the previous pick, shown as a row of removable swatches -- adjust a
-	shared tolerance, and see a live checkerboard-backed preview of the
-	result before committing. A self-contained modal dialog rather than
-	a diagram-level "click the canvas to pick" interaction mode, since
-	this needs neither undo-during-drag nor coexistence with other
-	tools; it only ever needs a handful of clicks, evaluated against a
-	pixmap the caller already has in hand.
+	the previous pick -- each shown as its own row: a colour swatch, a
+	slider for that colour's own tolerance right next to it, and a
+	remove button. Each colour keeps its own tolerance rather than
+	sharing one: a white background and a grey border rarely need the
+	same looseness of match, and forcing one tolerance onto both meant
+	either the background left ragged edges or the border ate into
+	content near it. A live checkerboard-backed preview of the combined
+	result updates as any slider moves. A self-contained modal dialog
+	rather than a diagram-level "click the canvas to pick" interaction
+	mode, since this needs neither undo-during-drag nor coexistence
+	with other tools; it only ever needs a handful of clicks, evaluated
+	against a pixmap the caller already has in hand.
 */
 class ImageTransparentColorDialog : public QDialog
 {
 	Q_OBJECT
 
 	public:
+		/// One picked colour and the tolerance it's individually keyed
+		/// with -- the whole point of this being a struct rather than
+		/// two parallel lists is that the two can never drift out of
+		/// index alignment with each other.
+		struct PickedColor
+		{
+			QColor color;
+			int tolerance;
+		};
+
 		/// @param basePixmap the pristine source to pick colours from --
 		/// the caller's responsibility to pass the true original, not
 		/// an already colour-keyed result, or previously-transparent
 		/// areas would show as plain background rather than a pickable
 		/// surface, and re-picking the same colour would be a no-op.
-		/// @param existingColors colours already keyed out of basePixmap
-		/// in a previous session, shown as swatches from the start
-		/// rather than forcing them to be re-picked from scratch.
-		/// @param existingTolerance the tolerance from that previous
-		/// session, if any.
-		explicit ImageTransparentColorDialog(const QPixmap &basePixmap, const QList<QColor> &existingColors = {},
-				int existingTolerance = 10, QWidget *parent = nullptr);
+		/// @param existingColors colours (with their individual
+		/// tolerances) already keyed out of basePixmap in a previous
+		/// session, shown as rows from the start rather than forcing
+		/// them to be re-picked from scratch.
+		explicit ImageTransparentColorDialog(const QPixmap &basePixmap,
+				const QList<PickedColor> &existingColors = {}, QWidget *parent = nullptr);
 
 		/// The resulting pixmap: basePixmap unchanged if no colour is
-		/// picked, colour-keyed against every picked colour otherwise.
+		/// picked, colour-keyed against every picked colour (each at
+		/// its own tolerance) otherwise.
 		QPixmap resultPixmap() const;
-		/// The final set of picked colours, for the caller to remember
-		/// across dialog sessions -- may differ from existingColors if
-		/// any were added or removed.
-		QList<QColor> pickedColors() const { return m_pickedColors; }
-		/// The final tolerance, for the same reason.
-		int tolerance() const { return m_tolerance; }
+		/// The final set of picked colours and their individual
+		/// tolerances, for the caller to remember across dialog
+		/// sessions -- may differ from existingColors if any were
+		/// added, removed, or had their tolerance adjusted.
+		QList<PickedColor> pickedColors() const { return m_pickedColors; }
 
 		/// Public so DiagramImageItem can re-derive its display pixmap
 		/// directly (base + crop + these colours) without needing to
 		/// re-open this dialog every time the crop region changes --
 		/// binary transparency within tolerance, not a smooth falloff:
-		/// every pixel within `tolerance` (0-100, mapped onto the
-		/// maximum possible RGB distance) of *any* of keyColors becomes
-		/// fully transparent, everything else keeps its existing alpha
-		/// untouched. Squared distance throughout, avoiding a sqrt per
-		/// pixel; breaks out of the inner loop on the first matching
-		/// colour, since further matches wouldn't change the outcome.
-		static QImage applyColorKey(const QImage &source, const QList<QColor> &keyColors, int tolerance);
+		/// every pixel within a colour's own `tolerance` (0-100, mapped
+		/// onto the maximum possible RGB distance) of that colour
+		/// becomes fully transparent, everything else keeps its
+		/// existing alpha untouched. Squared distance throughout,
+		/// avoiding a sqrt per pixel; breaks out of the inner loop on
+		/// the first matching colour, since further matches wouldn't
+		/// change the outcome.
+		static QImage applyColorKey(const QImage &source, const QList<PickedColor> &keyColors);
 
 	private slots:
 		void onColorPicked(const QColor &color);
-		void onToleranceChanged(int value);
 
 	private:
-		void removeColor(const QColor &color);
+		void setToleranceForIndex(int index, int value);
+		void removeColor(int index);
 		void rebuildSwatches();
 		void updatePreview();
 		static QPixmap onCheckerboard(const QImage &image);
 
-		QImage        m_sourceImage;
-		QList<QColor> m_pickedColors;
-		int           m_tolerance = 10;
+		QImage              m_sourceImage;
+		QImage              m_previewSourceImage;   // downsampled -- see ClickableImageLabel::displayImage()'s comment for why
+		QList<PickedColor>  m_pickedColors;
+		int                 m_lastToleranceUsed = 10;   // seeds a newly-picked colour's own tolerance, so successive picks in one session feel consistent rather than each resetting to some fixed default
 
 		ClickableImageLabel *m_sourceLabel;
 		QLabel              *m_previewLabel;
-		QHBoxLayout         *m_swatchesLayout;
+		QVBoxLayout         *m_swatchesLayout;   // one row per picked colour, stacked vertically -- each row now carries its own slider, too wide to lay out side by side the way plain swatches once were
 		QLabel              *m_hintLabel;
-		QSlider             *m_toleranceSlider;
 		QPushButton         *m_okButton;
 };