When I got my Macbook about 9 months ago one of the first things I did was change the default OSX screenshot format type from PNG to GIF. I edit a lot of images in Photoshop to post in technical articles and for the GIF’s I have been having to change the Photoshop Image Mode from Indexed Color to RGB to apply most filters during the process of editing the image. Photoshop loses a lot of functionality when an image’s Image Mode is set to Indexed so each time I modified an screenshot image and say wanted to apply a filter I would first have to modify the Photoshop Image Mode from Indexed Color to RGB. I recently got fed up with having to do that so I was looking for a solution when I realized if I just change the default screencapture format back to PNG the images open in Photoshop with the Image Mode set to RGB or Red/Green/Blue Color Model. Anyhow when doing so I started to wonder what image formats were available to set as the default screencapture format. Below I describe the details of what screencapture image formats are available in Mac OSX Lion and also what Image Mode that Adobe Photoshop opens each format from the Mac in.
I was attempting to save a file at 16 color 4 bit depth using Photoshop 4 on a Windows XP laptop. After creating or modifying the image and attempting to save the file as a bitmap (.bmp) the bitmap options would popup though I was unable to choose 4 bit under the depth option. I figured the image may have to many colors and decided to try to switch the “Image Mode” to Grayscale.
ImageMagick is a really cool product. Not only is it open source but its very powerful tool. My goal was to figure out how to batch resize images while keeping one side 640 pixels wide. I ended up using ImageMagick’s mogrify by issuing the command below at my CentOS shell prompt.
mogrify -resize x640 *.jpg
mogrify -resize 640 *.jpg
Depending on which side you want to be 640 pixels. If you would like for image magic to make the largest side 640 and constrain the proportions use the following command.