The Intel® Graphics Performance Analyzers (Intel® GPA) developer tool suite provides a complete toolkit for analyzing and optimizing your games, media, and other graphics-intensive applications.
One of the tools in the product, Intel® GPA Frame Analyzer, allows you to save a render target image to disk for analysis with other programs (such as Adobe Photoshop* or Microsoft Paint*). When using PNG format the saved image may not match what's displayed within Intel GPA Frame Analyzer.
This article describes why the images don't necessarily match, and how to get the results you want.
The Short Answer
In Intel® GPA Frame Analyzer, when you right-click an image in the render target viewer, you can save the image in one of three formats: JPG, BMP, and PNG. The first two options (JPG and BMP) store only the RGB values, but the PNG format stores both the RGB and Alpha channel data. So right away you can see a potential issue: when using PNG format, the image displayed depends upon whether the image contains any Alpha channel data and how your graphics viewer treats the Alpha channel data.
So for most users here's a simple solution: Always save your render target images as JPG or BMP format, as this guarantees that the image in Intel GPA Frame Analyzer matches the image displayed with programs such as Microsoft Paint*.
The Long Answer
Intel® GPA Frame Analyzer allows you to select a render target from the Render Target Viewer, and see the image for that render target in the space to the right. A "hidden" feature (since it's not included in the Help File) is to right-click in the image area, which displays an option to save the render target image to disk:
For "Save..." options, the choices are JPG, BMP, or PNG formats. If you view the JPG or BMP files in a program such as Adobe Photoshop*, here's what you'll see (note the display matches what is displayed in the Intel GPA Frame Analyzer):
Viewing the PNG file in Adobe Photoshop*, note the checkerboard pattern I've highlighted in the upper left-hand corner of the screen:
So for most users we recommend that you use the BMP and JPG formats -- the displayed image within your viewer matches what's displayed in the render target viewer.
However, you may be an advanced user who needs the extra Alpha channel data -- if so, experiment using the PNG format.
One last thing -- you can change the image format displayed in the Render Target Viewer by using the Histogram panel (it's on the far right side of the Render Target Viewer -- double-click to open it). The default is RGB, but you can also view the image in RGBA, Grayscale, or the individual red, green, and blue channels as well.
Where to Next...
If you want to experiment yourself before determining which format to use, I've attached some image files exported from Intel GPA Frame Analyzer (sample.bmp, sample.jpg, and sample.png). This particular image contains Alpha data, so it's a good test case. Therefore, use your favorite image viewer to see the differences for what's displayed with each format.
If you have any problems using this feature, please let us know in the Intel GPA Support Forums. Also, use the Support Forums to leave the Intel GPA team comments or suggestions about the product -- we would love to hear from you!
* Other names and brands may be claimed as the property of others.