Imagination PowerVR SDK Blog

Using JPEG images with SDK

pvrtextool

#1

I am using the OpenGLES1 SDK , which I downloaded from your website. I have JPEG images that I wish to use at textures. I think PVRTools can only load PVR files. Is that correct? How can I load JPEG files with the SDK?





Thanks,


Emma
























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#2

JPEG files are unsuitable to use directly as textures with graphics acceleration, please see our FAQ for an explanation: "Why should I use PVRTC instead of PNG/JPG for my application and what’s the difference among the formats?"

https://www.imgtec.com/powervr/insider/powervr-faq.asp

I suggest converting to the .pvr format using PVRTexTool - note that .pvr files can contain any of the OpenGL ES 1.1 formats as well as PVRTC. PVRTC will give you the best performance, but if you’re not happy with the compression quality of specific textures you can choose a higher bitrate format (RGB565, ARGB4444, RGB888, ARGB8888) for these textures and the PVRTools code will load them with the same function call.


#3

Just to add to what Gordon has said, JPEG is also a lossy compression system and so will introduce some unwanted artefacts of its own. If you then try to compress those images with, say, PVRTC, the compressor can’t tell what was meant to be in the source image and what were JPEG errors and so will likely compound the JPEG errors with its own errors.

If you only have access to JPEG images, I suggest you always try to get hold of the highest resolution versions you can, downsize them in your favourite image editor to the required size, and then save them in a lossless format like PNG.  Then, use those as source images for the compressor.

Simon