The Three Principles
Speeding Up Image Load Times
The main idea behind making an image load faster is to make the file size smaller. The smaller the image, the smaller the file size. Imagine an image that is a square 80 pixels by 80 pixels. The number of pixels contained in the image is 80x80 or 6400 individual pixels. If we reduce the image size by one half to 40 pixels by 40 pixels we then have 40x40 or 1600 pixels. So reducing the image size in half reduces the file size to one fourth of the original.
This is our First Principle of Image File Size Reduction: Use the smallest image dimensions that will work with your layout.
GIF images are limited to 256 colors per image, are better at displaying images with large solid blocks of color and images with very small physical dimensions. The GIF format will produce smaller file sizes than JPEG for these types of images.
JPEGs reproduce photographs very well. The JPEG format will produce smaller file sizes for these types of images than the GIF format will.
This is our Second Principle of Image File Size Reduction: Choose the correct image format for the image you are using. Most web pages will contain a combination of GIF and JPEG images.
Decreasing the coding is called image compression. Both GIF and JPEG images can be compressed but the process is different. In GIF images we try to limit the number of colors, in a JPEG image we use software algorithms to remove redundant information from the file.
This is our Third Principle of Image File Size Reduction: Find the least acceptable level of image quality. Most images can handle some compression with very little quality loss, and all images can stand more image quality loss and still be acceptable. Your job is to decide how much quality loss you can accept. In other words, the lower the quality, the smaller the file size.
GIF images can usually be reduced from 256 colors to 128 colors or less, the fewer colors used the smaller the file size. JPEG images can almost always be reduced to a quality setting of 80% and frequently can be reduced down to as little as 15-30%.
Source: http://www.sitepronews.com/archives/2005/july/8.html
The main idea behind making an image load faster is to make the file size smaller. The smaller the image, the smaller the file size. Imagine an image that is a square 80 pixels by 80 pixels. The number of pixels contained in the image is 80x80 or 6400 individual pixels. If we reduce the image size by one half to 40 pixels by 40 pixels we then have 40x40 or 1600 pixels. So reducing the image size in half reduces the file size to one fourth of the original.
This is our First Principle of Image File Size Reduction: Use the smallest image dimensions that will work with your layout.
GIF images are limited to 256 colors per image, are better at displaying images with large solid blocks of color and images with very small physical dimensions. The GIF format will produce smaller file sizes than JPEG for these types of images.
JPEGs reproduce photographs very well. The JPEG format will produce smaller file sizes for these types of images than the GIF format will.
This is our Second Principle of Image File Size Reduction: Choose the correct image format for the image you are using. Most web pages will contain a combination of GIF and JPEG images.
Decreasing the coding is called image compression. Both GIF and JPEG images can be compressed but the process is different. In GIF images we try to limit the number of colors, in a JPEG image we use software algorithms to remove redundant information from the file.
This is our Third Principle of Image File Size Reduction: Find the least acceptable level of image quality. Most images can handle some compression with very little quality loss, and all images can stand more image quality loss and still be acceptable. Your job is to decide how much quality loss you can accept. In other words, the lower the quality, the smaller the file size.
GIF images can usually be reduced from 256 colors to 128 colors or less, the fewer colors used the smaller the file size. JPEG images can almost always be reduced to a quality setting of 80% and frequently can be reduced down to as little as 15-30%.
Source: http://www.sitepronews.com/archives/2005/july/8.html
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