To avoid server errors when managing photos in Joomla, it's important to ensure that all images (a) are relatively small in filesize (i.e. 2MB or less) and (b) are relatively low-resolution (i.e. heights and widths of 2000 pixels or less.) Any image editor can be used to resize photos, but a handy free tool available for PC, Mac and Linux calledXnConvert makes photo preparation quick and painless. This tutorial assumes you have installed XnConvert and have launched the program.
Add Files to select specific images, or click Add folder... to select an entire folder. You will then be prompted to browse your computer and select the images.
In the Input area, you will see the photos you have selected.
Next, click on the Actions tab and click on the Add Action icon.
Image and then Resize.
From the Presets dropdown menu, select a size. For web photo galleries, 1600x1200 is perfect (your Joomla photo gallery software, such as Phoca Gallery, will further reduce the size later to make thumbnail images etc.) Be sure to also select Reduce Only (if you happen to have selected any small images, they will look terrible if enlarged!)
Click on the Output tab and then on the ellipsis icon (i.e. three dots) to select a folder where the resized images should go. TIP: Place them in an easy-to-find location, such as a folder on your desktop.
Finally, click Convert to resize your images.