Detailed PNG pictures

1. png Picture type

The PNG format has 8-bit, 24-bit, 32-bit three, and the following are some of the terms:

Index transparency: Similar to GIF, a pixel is only full and opaque two effects alpha transparent: Translucent PNG8

8-bit PNG supports up to 256 (2 8) colors, and 8-bit PNG supports index transparency and alpha transparency.

PNG24

Supports 2 of 24-time color, but does not support transparent information.

PNG32

The 32-bit PNG adds 8-bit transparent information to 24-bit PNG, and therefore supports varying degrees of semi penetration.

Summarize

pnG32

format	color type	number	transparent support
png8	2 's 8-second party	8
png8+ index transparency		8	only fully or completely opaque
png8+alpha Transparent	2 8 times	supports semitransparent
png24	2 's 24-time side	24
2 's 32-second party	32	support semi-transparent

2, graphics processing software Fireworks

In fireworks, the various formats mentioned above can be generated correctly, as long as you select the appropriate format in the Optimize panel.

Photoshop

In Photoshop (PS), the PNG format selection can be implemented by selecting the Save for Web & devices of the File menu, noting:

PS does not support 8-bit png+alpha transparent format; There is no 32-bit PNG option in PS, but png24+ transparency is actually PNG32.

3, browser support situation

IE6 is not supported for PNG8 and PNG32 translucent effects, with filters to resolve PNG32 semi-transparent problems, but not PNG8 translucent effects.

Let's test the browser's support for transparent PNG, where IE6 uses filters to load PNG pictures. The remaining browsers use the IMG tag. After testing, found that the IE6 browser performance is consistent, and IE6 to Png8+alpha transparent support is not good enough, the translucent part of the image is completely transparent way to deal with. The test results are shown in the following illustration:

4, summary

The 1.PNG format has 8-bit, 24-bit, 32-bit three forms.

8-bit PNG supports two different forms of transparency (index transparency and alpha transparency);

24-bit PNG does not support transparency;

The 32-bit PNG adds 8-bit transparent channels on a 24-bit basis, thus displaying a level of level 256 transparency.

2. Picture Processing Tools

Photoshop: Png8+alpha Transparent PNG is not supported or exported;

The PHOTOSHOP:32 bit PNG output is output by 24-bit PNG plus transparent information;

Fireworks: Good for PNG support.

3. Browser support

Non-IE6 browsers can display PNG pictures that contain transparent information, including index transparency and alpha transparency;

IE6 with the help of the filter to PNG32 transparent PNG image under IE6 whether or not to use a filter, the translucent part is completely in full transparency manner;

IE6 is not good enough for png8+alpha transparent image support.