Description

SetBgImage sets an image file to be used as the graph background. The image can be scaled or tiled to fit.

Parameters

Notes

If a background image has been set, background color (set with SetBackgroundColor) is ignored.

Scale mode scales the supplied background image file to fit the image area of the entire graph. Tile and centeredtile modes repeat the supplied background image file as needed to fit the image area of the graph. The difference is that centeredtile offsets the start position within the background image by half its size, which works better for some images.

SetBgImage sets a background for the entire image area, while SetPlotAreaBgImage sets a background for the plot area (generally, the area between the axes). If both are used, the plot area background overlays that portion of the overall background.

If $input_file is NULL, no background image will be used.

If you are going to use a JPEG file for the image background, you should be using a truecolor PHPlot image. Truecolor images do not have a limited-size color map like palette images (which PHPlot uses by default). If you use palette image with a JPEG background, the background will likely overflow your image's color map and leave no free color slots for PHPlot to use for plot elements. The same is true if using a 24-bit color (non-mapped) PNG file for a background if it has many colors. For more on truecolor PHPlot images, see Section 4.3, “Truecolor Images”.