[email protected] wrote:
> Hi,
>
> I am trying to modify HSV values of a Qimage and am finding dithered
> edges in the modified image after manipulating the pixels.
> Can you provide some pointers on how to fix this issue. My code is given
> below ...
>
> public QImage applyImageFilter(final QImage origimg) {
> // img is the original image and img1 is the resultant img
> QImage img1 = new QImage(80, 80, QImage.Format.Format_ARGB32);
> img1.convertToFormat(QImage.Format.Format_ARGB32,
> ImageConversionFlag.AlphaDither_Mask);
This code makes little sense... First you create the pixmap with ARGB32
format, then convert it to ARGB32 format? This is a redundant operation
and should be removed.
> img1.fill(QColor.transparent.value());
> QPainter p = new QPainter(img1);
> QSvgRenderer svgrenderer = new QSvgRenderer();
> p.setRenderHint(QPainter.RenderHint.Antialiasing, true);
>
> for (int i = 0; i < 80; i++) {
> for (int j = 0; j < 80; j++) {
> int col = origimg.pixel(i, j);
> if (col == 0) {
> continue;
> }
> QColor qcol = new QColor(col);
> qcol.setHsvF(0.0, 1.0, 0.5, 1.0);
> QPen pen = new QPen(qcol, 1.0, PenStyle.SolidLine,
> PenCapStyle.FlatCap, PenJoinStyle.RoundJoin);
> p.setPen(pen);
> p.drawPoint(i, j);
Using a painter for this is overkill and in addition to being a lot more
expensive... why not just:
img1.setPixmap(i, j, qcol.argb());
> }
> }
> p.end();
> svgrenderer.render(p);
> return img1;
> }
The reason you have artifacts along the edges of your image is because
you are drawing with anti-aliasing. A complete description of the
coordinates system is covered here:
http://doc.trolltech.com/qtjambi-4.4/html/com/trolltech/qt/coordsys.html
but you probably just want to use QImage::setPixel().
best regards,
Gunnar
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