The problem with converting a jpg file to an intensity graph is that a jpg generally consists of rgb values, so an image really has three intensities (you could certainly combine these in some manner if you wanted). The best place to start would be with Read JPEG File and then Unflatten Pixmap VIs.
The biggest challenge you will run across is that a jpg file can be represented in a number of ways (image depths). If you have LV 7.1, I recommend that you wire a true to the "use 8-bit color table" input on Read JPEG file, and then use the 8-bit pixmap output of the unflatten from pixmap. Each value in this pixmap array will be an index into the colors array (another output of the unflatten from pixmap) and each value in the colors array is a color, wh
ich you can use the color to RGB VI on in order to get the red, green and blue intensities. You can then construct a 2-d array out of one of these values (or combine them mathematically) and wire it into an intensity graph.
If you have LV 7.0 or earlier you'll have a little more trouble, as you'll need to use a case structure to handle each image depth (you can unbundle the image cluster to get the image depth). The 8-bit depth will be the same as described previously, and the 4 and 1 bit depths will be similar, but the 24 bit (which most JPEG files use) doesn't use the Colors table, and requires a little byte manipulation to get the R, G and B values.
I've attached examples in both LV 7.0 and LV 7.1 (the LV 7.0 one only handles 8 and 24 bit pixmaps, but the 1 and 4 bit ones are pretty rare, and easy to implement if you need them). Each one gives a file select for the image and then displays three intensity graphs, one for each primary color.
Regards,
Ryan K.
