Exporting images¶

PlotExporter captures a plot as a raster image:

import QAccelPlot as QAccelPlot

QAccelPlot.PlotExporter {
    id: exporter
    plot: plot
    scale: 2
    onFinished: (ok, path, error) => console.log(ok ? "Saved " + path : error)
}

Button {
    text: "Save"
    enabled: !exporter.busy
    onClicked: exporter.save("plot.png")
}

Method	Result
`save(path)`	Writes a file in the format the suffix names. `path` may be a `file:` URL from a `FileDialog`.
`copyToClipboard()`	Puts the image on the clipboard.
`grabImage()`	Emits `imageReady(image)` with a `QImage`.
`supportedFormats()`	Lists the suffixes `save()` accepts, such as `png`, `jpg`, `bmp`, `webp`, `tif`. Image format plugins decide which are present.

The image contains the plot item and everything inside its bounds as shown on screen: series, axes, the legend, overlays, and child items.

Options¶

Property	Default	Meaning
`scale`	`0`	Image pixels per logical pixel. `0` uses the window's device pixel ratio, so the image matches the screen. The layout does not change: a 2× image has the same ticks and text positions, drawn at twice the resolution. At a device pixel ratio other than 1, a side can differ by one pixel from its size × scale.
`quality`	`-1`	0–100, passed to `QImageWriter`. `-1` uses the format's default. JPEG and WebP trade size for artifacts; PNG stays lossless.
`dpi`	`0`	Resolution stored in the file. `0` stores 96 × scale, so documents place the image at its on-screen size.
`transparentBackground`	`false`	Leaves out `axesAreaColor` and `plotAreaColor`, so the image takes the background it is placed on. The grid, series, axes, and legend are drawn as usual.

Formats without an alpha channel, such as JPEG and BMP, composite transparent pixels over white. For a light image of a dark-themed plot, bind its colors to Colors.light before exporting, as the Theming example does.

Requests¶

Each request ends with one finished(ok, path, error). path is empty except for save().
A request made while busy only returns false and warns; finished() stays with the request in progress.
The capture happens on the next frame. It fails if the window is hidden, minimized, or destroyed first. Encoding and writing the file run on a worker thread, and an existing file is replaced only once the new one is complete.
A request fails immediately, returning false, when another exporter is capturing the same plot, the file format is unsupported, the plot is hidden, has no size, or is not in a window, the window is hidden or minimized, the window uses the software backend, or the image would exceed the GPU's maximum texture size.
With transparentBackground set, the plot shows no background for the one frame the capture is taken in.

C++¶

auto* exporter = new QAccelPlot::PlotExporter(this);
exporter->setPlot(plot);
exporter->setScale(3.0);
connect(exporter, &QAccelPlot::PlotExporter::imageReady, this, [](const QImage& image) {
    // Use the image on the UI thread.
});
exporter->grabImage();

Complete source: examples/data/export