Microsoft Office Tutorials and References
In Depth Information
Exploring the Many Types of Pictures
Exploring the Many Types of Pictures
The world is awash with many different picture file formats. Fortunately,
PowerPoint works with almost all these formats. The following
sections describe the two basic types of pictures that you can work with in
PowerPoint: bitmap pictures and vector drawings.
Bitmap pictures
A bitmap picture is a collection of small dots that compose an image. Bitmap
pictures are most often used for photographs and for icons and other
buttons used on web pages. You can create your own bitmap pictures with
a scanner, a digital camera, or a picture-drawing program, such as Adobe
Photoshop. You can even create crude bitmap pictures with Microsoft Paint,
which is the free painting program that comes with Windows.
The dots that make up a bitmap picture are called pixels. The number of pixels
in a given picture depends on two factors: the picture’s resolution and its size.
Resolution refers to the number of pixels per inch. A typical computer monitor
displays 72 pixels per inch, though many monitors can display at higher
resolutions. At 72 pixels per inch, a 1-inch square picture requires 5,184 pixels (72 x
72). Photographs that will be printed on an inkjet or laser printer usually have
a much higher resolution, often 300 pixels per inch or more. At 300 pixels per
inch, a 4-x-6-inch photograph requires more than two million pixels.
The amount of color information stored for the picture — also referred to as
the picture’s color depth — affects how many bytes of computer memory the
picture requires. The color depth determines how many different colors the
picture can contain. Most pictures have one of two color depths: 256 colors or
16.7 million colors. Most simple charts, diagrams, cartoons, and other types of
clip art look fine at 256 colors. Photographs usually use 16.7 million colors.
Pictures with 16.7 million colors are also known as True Color pictures or
24-bit color pictures.
A 4-x-6-inch photograph, which has more than 2 million pixels, requires about
2MB to store with 256 colors. With True Color, the size of the picture jumps
to a whopping 6.4MB. Fortunately, bitmap pictures can be compressed to
reduce their size without noticeably distorting the image. Depending on the
actual contents of the picture, a 6MB picture might be reduced to 250KB or less.
Bitmap picture files usually have filename extensions such as .bmp, .gif, .jpg,
.png, or .pcx. Table 11-1 lists the bitmap file formats that PowerPoint supports.
If you have a choice in the matter, I recommend you use JPEG format images
for photographs that you want to include in PowerPoint presentations
because JPEG’s built-in compression saves hard drive space.
 
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