PDA

View Full Version : Linear Filtering, Brightness and Contrast



Bumbala
02-05-2006, 10:12 PM
Hi,

I render raster images as quads which are connected to each other forming a grid.

1. When I apply linear filtering, a visible grid is formed on the edges. I want smooth edges.

2. I want to set brightness and contrast of these textures.

Can anybody help me?
Thanks!

02-06-2006, 07:21 AM
1. Have you tried point filtering?

2. What kind of contrast stretching are you interested in. There's a simple min/max normalization or there's histogram based techniques and others. What do you mean by brighten? Simply increase the RGB in the image or something fancier?

Cheers

:)

Purvis
02-06-2006, 08:45 AM
1) Try using GL_CLAMP_TO_EDGE extension, I understand it solves some artifacts in edges with filtering, like for a skybox for example. Honestly I never used it.

2) Isn't there an imaging API for those kind of things since 1.2? Otherwise you can use fragment programs but you'll need a good gfx card.

Bumbala
02-06-2006, 10:48 AM
1. GL_CLAMP_TO_EDGE solved the problem, thank you.

2. The scene is a simple orthographic projection. I render the tiles of a tiff image as quads. I call glColor3ub(255, 255, 255) before rendering. I may adjust this color but it is not actually a brightness or contrast adjustment. I don't need image editing capabilities. I just need to darken or lighten the scene a bit.