From BlenderWiki

Image Textures

Description

If you choose the Texture Type Image in the Texture Panel, the Map Image and Image panels appear, allowing you to control most aspects of image textures and how they are applied.

The term, "image texture," simply means that a graphic image (composed of R, G, B and perhaps Alpha information arranged in pixels) is used as the basic source of input to the texture. As with any other type of texture, this data can be used in any number of ways ... not just as, say, a "decal."

Map Image Panel Options

This panel controls what aspects of the image are used, how it is to be mapped to the underlying material, and controls whether it is to be offset from its origin, and whether it should be repeated or stretched to fit.

These two different images are used here to demonstrate the different Map Image options. The background image is an ordinary JPG-file, the foreground image is a PNG-file with various Alpha- and Greyscale values. The vertical bar on the right side of the foreground image is an Alpha blend, the horizontal bar has 50% Alpha.}}

MipMap

MipMaps are precalculated, smaller, filtered Textures for a certain size. A series of pictures is generated, each half the size of the former one. This optimizes the filtering process. By default, this option is enabled and speeds up rendering (especially useful in the game engine). When this option is OFF, you generally get a sharper image, but this can significantly increase calculation time if the filter dimension (see below) becomes large. Without MipMaps you may get varying pictures from slightly different camera angles, when the Textures become very small. This would be noticeable in an animation.

Gauss

Used in conjunction with MipMap, it enables the MipMap to be made smaller based on color similarities. In the game engine, you want your textures, especially your MipMap textures to be as small as possible to increase rendering speed and framerate.

InterPol

This option interpolates the pixels of an Image. This becomes visible when you enlarge the picture. By default, this option is on. Turn this option OFF to keep the individual pixels visible and if they are correctly anti-aliased. This last feature is useful for regular patterns, such as lines and tiles; they remain 'sharp' even when enlarged considerably. When you enlarge this 10x10 pixel Image , the difference with and without InterPol is clearly visible (Enlarged Imagetexture). Turn this image off if you are using digital photos to preserve crispness.

Rot90

Rotates the Image 90 degrees counterclockwise when rendered.

UseAlpha

Works with PNG and TGA files since they can save transparency information (Foreground Image with UseAlpha). Where the alpha value in the image is less than 1.0, the object will be partially transparent and stuff behind it will show.

CalcAlpha

Calculate an alpha based on the RGB values of the Image. Black (0,0,0) is transparent, white (1,1,1) opaque (Foreground Image with CalcAlpha). Enable this option if the image texture is a mask. Note that mask images can use shades of gray that translate to semi-transparency, like ghosts, flames, and smoke/fog.

NegAlpha

Reverses the alpha value. Use this option if the mask image has white where you want it transparent and vice-versa.

Filter

The filter size used in rendering, and also by the options MipMap and Interpol. If you notice gray lines or outlines around the textured object, particularly where the image is transparent, turn this value down from 1.0 to 0.1 or so.

Normal Map

This tells Blender that the image is to be used to create the illusion of a bumpy surface, with each of the three RGB channels controlling how to fake a shadow from a surface irregularity. Needs specially prepared input pictures. See section Bump and Normal Maps.

Usually, an image texture will fit the entire size of the texture space. Similarly to the NoiseSize options in procedural textures, you can also change the scaling and positioning of image textures, within the texture itself, before it is mapped.

Extend

Outside the Image the colour of the edge is extended (Extend). The Image was put in the center of the object with the shown settings.

Clip

Outside the Image, an alpha value of 0.0 is returned. This allows you to 'paste' a small logo on a large object.

ClipCube

The same as Clip, but now the 'Z' coordinate is calculated as well. Outside a cube-shaped area around the Image, an alpha value of 0.0 is returned.

Checker

Checkerboards quickly made. Mortar governs the distance between the checkers in parts of the texture size.

(You can use the option size on the Map Input Panel as well to create the desired number of checkers).

Mirror

The two Mirr buttons allow you to map the texture as a mirror, or automatic flip of the image, in the corresponding X and/or Y direction.

Repeat

The Image is repeated horizontally and vertically as often as set in Xrepeat and Yrepeat.

MinX, MinY, MaxX, MaxY

The offset and the size of the texture in relation to the texture space. Pixels outside this space are ignored. Use these to crop, or choose a portion of a larger image to use as the texture.

Image Panel Options

Load Image

• Load a single image file in one of Blender's supported file formats: BMP, JPG, PNG, TGA, TIFF, OpenEXR, Cineon, DPX and Radiance HDR. Others, like PSD and GIF - are partially supported via QuickTime on Windows and Mac versions.
• To use a vector format SVG image, use the Vectrex texture plugin
• Load an animation as a numbered image sequences in any of the supported image file formats. To do this, first click on the first frame and then Load file. Then change the Image type to Sequence, and enter the ending frame number
• Load an animation as an avi or mov file. Accepted are uncompressed or JPG compressed AVIs. On Windows and Mac with QuickTime, most quicktime movies should work, and on Windows platforms all videos with a supported codec should work.

For any of the above, you can use absolute as well as Relative Paths. The // (double Backslash) means the working directory, .. (two dots) point at the parent directory. Select relative or absolute in the file browser window header.

Movie

Movie files (AVIs supported by Blender, SGI-movies) and "anim5" files can also be used for an Image texture. In this case the subsequent Panel, Anim and Movie is populated by Buttons.

IM

The internal name of the IMage. Use the select button to rapidly change between textures loaded into memory. ⇧ ShiftLMB click into the field to give the image a meaningful name

Reload

Load the image again from disk (i.e. if it's been changed in an external application)

X

Delete the link from this texture to this image

Users

The number of other materials that use this image. Click to make the information about this image local to this instance of use.

Pack ( )

Saves the still or generated image inside the blend-file. Use this if you are mailing or sharing .blend files between PC's with different directory structures.

The text below the filename provides information about the file

Fields

Video frames consist of two different images (fields) that are merged by horizontal line. This option makes it possible to work with field images. It ensures that when Fields are rendered the correct field of the Image is used in the correct field of the rendering. MipMapping cannot be combined with Fields.

Odd

Normally, the first field in a fielded (interlaced) video frame begins on the first line. Some frame grabbers do this differently.

Anti

Graphic images such as cartoons and pictures that consist of only a few colors with a large surface filling can be anti-aliased as a built in pre-process. This is not useful for Photos and similar pictures. Needs OSA.

Auto Refresh

When you change frames, blender gets the latest image from the sequence or codec.

Frames

How many frames of the animation to use; the length of the segment

Offs

What frame number inside the movie/sequence to start grabbing

Fie/Ima

Fields per Image. Used with Fields and interlaced video, it says whether each image has both odd and even, or just one.

StaFr

Starting Frame - when the animation reaches this frame number, the movie/sequence will start playing

Cyclic

When the video ends, it will loop around the to the start and begin playing again.

Seamless Images

When an image is repeated, the left side of the repeat copy is mushed up against the right side. Similarly, when repeating upwards, the bottom of the second copy is placed against the top of the first. Where they meet, a seam may show if the pixels of one side do not line up with the other. You want image textures to be seamless, so that when viewed side by side, the repeating is not detectable. The best example of this is a brick texture. Use an image texture of a few bricks where the boundaries of the image align at the top and bottom on the mortar, and the left and right edges evenly split a brick, and that the left brick matches up nicely with the far right brick. This concept applies to terrain (outside grass, sidewalks, pavement), flooring (inside wood, stone, tile), tree bark, animal skins, roofing shingles of all types, cloth and fabric designs, wallpaper designs, dirty surfaces, sidewalks, and almost all exterior building surfaces (continuous, siding, shingle, brick, stone veneer). Both images to the right were tiled 2 times across and 3 times vertically.

When working with existing images to make them seamless, try to correct any skewing based on camera angle; you want an image taken "straight on", because the program will repeat the image flat onto the surface. Also pay attention to lighting; you want a flat light across the surface, because if the left side is lighter than the right, when they are placed together, there will be a noticeable difference.

Some paint programs have features to help you. For example, GIMP has a map filter to Make Seamless any image. It also has tools like Threshold that show you any lighting differences.

Also, placing a prop in front of a seamed wall really fakes out the eye from detecting a pattern. A simple table and lamp or chair for inside walls, or a plant or person or car for outside really helps deflect attention from percieving a repeating pattern.