Halo CE Bitmap compression stuff

1

Guerilla Group:

Compression
name:

Pixel
size:

File
size:

Colour depth:

rgb
setup:

alpha
setup:

Colours:

Photoshop export names:

2

DXT: 4x4 pixel texels reduced to 2 interpolated colours

A

R

G

B

RGB

3

Compressed with colour-key transparency

DXT1

4bits

1/8

-

5bit

6bit

5bit

16bit

2 sets per texel*

none

65536

DXT1 RGB 4 bpp | no alpha

4

Compressed with explicit alpha

DXT3

8bits

1/4

4bit

5bit

6bit

5bit

16bit

2 sets per texel*

explicit (per pixel)

65536

DXT3 ARGB 8 bpp | explicit alpha

5

Compressed with interpolated alpha (smooth alpha)

DXT5

8bits

1/4

4bit

5bit

6bit

5bit

16bit

2 sets per texel*

65536

DXT5 ARGB 8 bpp | interpolated alpha

6

16bit:

A

R

G

B

RGB

7

r5g6b5

16bit

1/2

-

5bit

6bit

5bit

16bit

explicit (per pixel)

none

65536

5.6.5 RGB 16 bpp | unsigned

8

a1r5g5b5

16bit

1/2

1bit

5bit

15bit

explicit (per pixel)

32768

1.5.5.5 ARGB 16 bpp | unsigned

9

a4r4g4b4

16bit

1/2

4bit

12bit

explicit (per pixel)

4096

4.4.4.4 RGB 16 bpp | unsigned

10

32bit:

A

R

G

B

RGB

11

x8r8g8b8

32bit

1/1

-

8bit

24bit

explicit (per pixel)

none

16777216

X.8.8.8 XRGB 32 bpp | unsigned

12

a8r8g8b8

32bit

1/1

8bit

24bit

explicit (per pixel)

16777216

8.8.8.8 ARGB 32 bpp | unsigned

13

14

Alpha

15

Red

*interplolated using two more sets generated during runtime

16

Green

17

Blue

18

RGB SUM

19

Tips:

20

You can shave half of the size off of a 32bit texture by halving the lenght of one of the axis,
this makes it take up the same amount of space as a 16bit texture with the size that it had before the rescale.
And, it might end up looking better than converting it to 16bit because of the improved colourdepth.

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A 32bit normal map at half the size can look nicer than a dxt3/5 at full size, because the normals are more smooth.
If there is no need for an alpha you can try 16bit r5g6b5 to half the size even more without losing too much colourdepth in more flat normal maps. Like ones generated from height maps.

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