www.codelegend.com/screenimp/tutorials/tutorial3

Screen Imp:
Tutorial 3

Can I save the picture so that the file is smaller than a Bitmap file?

Since some file formats actually lose information from the picture, a set of original pictures are best kept in a format that has no loss of information. Bitmap and PNG files store the original image, JPG files do not, even with quality set to maximum.

Setting the JPG Quality option to maximum. The JPG file is already small, reducing the image quality will make the file even smaller.

Setting JPG Options Adjusting JPG quality from the settings window

Bitmap images can be reduced in colour depth to reduce the file size. For example, 24 bit images can be converted to 8 bit, 256 colour images. This will not help JPGs because they are saved with 24bit information.

Setting the Colour Bit Depth. Other settings allow Grey Scale and Dithering modes to be chosen.

Setting Colour Depth Selecting 8 bit colour as the alternative format

Setting to save files in the alternative colour format.

Setting to Save in the Alternative Format Choosing to save images in the alternative colour format

The magnification reveals less colours in the 256 colour result image. These images do not scale so well.

Lens shows detail after converting from 24 bit to 8 bit Lens shows the dithered effect that does not scale

A better way to reduce the file size of a screenshot with a lower colour depth, is to use a non-dithered mode. With your desktop set at 15 bits or more, try setting the lens to 8 bit non-dithered colour to see the effect.


More about the image file formats supported by Screen Imp

Screen Imp deals with the natural formats of the computer screen display. The screen display can be thought of as a Bitmap with pixel memory, from 1 bit (2 colours monochrome), to 24 bit (16 million colours). The 32 bit display is a 24 bit image, but with 8 bits of additional information.

To store the images as files, Screen Imp supports BMP, JPG, PNG, EMF, and WMF. If Screen Imp does not support the file format you need, images can be transferred from other applications with the Windows Clipboard. There are also many programs available that can batch convert between hundreds of file formats.

Bitmaps (BMP) are the native image format of Windows. They store the original image without making any changes to it, and so create the largest files.

The JPG picture file format can be used to make very small versions of a Bitmap picture. However, the JPG format will lose information (picture quality), due to the type of compression used to make the file smaller. The quality setting can be reduced to make even smaller JPG files.

When working with JPGs, it is often best to keep a set of untouched originals, in a format that does not lose picture information. Many working sets can then be made from the original images.

The PNG picture file format can also be used to make smaller versions of a Bitmap picture. The PNG format does not lose information from the picture, but takes a little more time to process.

Metafiles (EMF, WMF) are not intended specifically to store Bitmap images. Metafiles normally contain information that describes the drawing process to create a picture. That information can be used to draw the picture at whatever scale and pixel resolution is needed.

For Metafile users, it should be noted that; Screen Imp supports Metafiles primarily for loading, viewing and printing the images. Screen Imp draws the Metafile picture onto an internal Bitmap, and saves this in a Metafile. The new Metafile has a single Bitmap stored in it, this is not the original description of the image.

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