![]() RGB is the only full-color model PNG supports. These features help to get accurate, consistent color on any calibrated monitor. PNG supports ICC color profiles, gamma correction, and white point. It's also possible to specify, without an alpha channel, that a particular pixel value means the pixel is 100% transparent. This lets you create an image that is shaped like a circle or oval, has holes in the middle, or has a completely irregular shape. Making some of an image's pixels 100% transparent means nothing will be drawn for those pixels. This allows two kinds of effects.Ī partial transparency level, such as 50%, lets one image seem to show through another. The alpha value for each pixel represents not a color, but a degree of transparency. Each pixel contains three values of 8 or 16 bits each, representing a value of red, green, and blue respectively.Ī grayscale or RGB image can have an alpha channel associated with it. The largest available pixel size is 16 bits. Each pixel holds a single color value, representing a shade of gray. ![]() Indexed color produces very small files when the image only needs a few colors. The maximum pixel size is 8 bits, so there can be up to 256 colors. Each pixel is an index into the color palette. The PNG format supports several color models: It lets the computer draw a low-resolution version of the image to start with, then add detail on subsequent passes until the user sees the highest quality image. This feature isn't used as often today as it was in the days of slow connections and processors. An interlaced PNG image reorders the data so it can be drawn in two or more passes while processing the data in sequence. It's hard to imagine a case where this wouldn't be enough. The image height and width can be as much as 2,147,483,648 pixels. They can even define new chunk types for their own use, and PNG readers that don't recognize the chunks will ignore them. File creators can define new metadata keys. The metadata can include the title, author, copyright, source, creation time, and more. The compression method, called "Deflate," is the same as a widely used ZIP compression method.Ī PNG file is made out of "chunks." They include the image data, information needed to draw it, and metadata describing the file. Photographic images and drawings with delicate color shadings won't benefit as much from PNG compression. It still compresses well when the image consists of solid chunks of color. This is different from formats like JPEG, which lose some low-order data bits for the sake of smaller file sizes. The original bits of each pixel can be recovered, bit for bit, by decompressing the file. "Lossless" means that the compression is fully reversible. Since then the format hasn't changed.Īll Web browsers that support graphics will display PNG files.Įxactly what is a PNG file? It's an image file using a lossless compressed image format. In 2003, the format became an ISO standard, with some minor revisions in 2004. The first version of the format definition came out in 1996. ![]() You can pronounce it "P-N-G" or "ping." Unlike GIF, which is limited to 256 colors, it supports full color and grayscale. They called it PNG, meaning Portable Network Graphics. TIFF was so loaded with features it had the same problem.Ī group of developers vented their frustration by creating a new, license-free format that was simple but powerful. JPEG didn't work well on the computers of the nineties. They weren't going to pay Unisys to post their graphics. But then Unisys started demanding license fees for the use of its patented compression algorithm. People could use it to create small image files, which was important when 2400 bps was considered a fast connection. Have questions or feedback about Office VBA or this documentation? Please see Office VBA support and feedback for guidance about the ways you can receive support and provide feedback.Before everyone was using the Internet, GIF images were popular on services like CompuServe. ![]() Not all controls support transparent bitmaps. You must use a picture editor such as Paintbrush to make a bitmap transparent. The BackColor property is only valid if the BackStyle property is set to 1.īackStyle does not affect the transparency of bitmaps. If BackStyle is 0, you can see through the control and look at anything on the form located behind the control. If BackStyle is 1, the control is not transparent and you cannot see anything behind the control on a form. The BackStyle property determines whether a control is transparent. 0 represents the background as transparent, 1 represents the background as opaque. SyntaxĮxpression A variable that represents an OptionButton object. Returns or sets an Integer that specifies the background style for an object. ![]()
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