I have hundreds of images each with size of more than 250 kb. How can I reduce the size of these images without quality loss? Which optimizer works best?
closed as not a real question by slhck Mar 11 '13 at 16:25
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What matters the most for images is which format you save them as, and the compression algorithm they use. (Extra note, the way to do this is to open them in most image editors, and to save them again, choosing the format you want.)
As a side note, JPEG is using a lossy compression already. Which means that you can reduce size by compressing more, by at the cost of quality. You can use JPEG with a quality factor of 100%, but then a PNG is more effective in size.
Gnoupi is not quite right, there are image optimizers. Those are special programs that focus on losslessly reducing the size of images by using techniques such as bit depth reduction, color type and color modification.
Here are some examples:
If you're looking for a very simple tool, without the need to install anything, use the online tool Smush.it, provided by Yahoo.
In some cases you can get a 10% size reduction, every bit is important! :-)
Without either turning down the quality or the image size, I don't think you can hope for much less size. But anyways, I can recommend IrfanView as it has a nice batch processor feature which you can use to change the format and/or size of several images in one go.
Depending on what you need the images for, I would ask myself how big I really need them and how good quality they need to be in. Using JPEG you can also turn down the quality a bit without it really being that noticable. Unless you are a perfectionist and can't live with anything but the best quality. And if that is the case, that you only can live with best quality, I would use the lossless PNG-24 format and not worry about the file size.
If you install the IrfanVew plugin pack as well, you'll get a plugin called PNGOUT which you can try out to compress the PNG files a bit extra.
one more thing to add, avoid using big size (pixels) images then resizing them in your html code.
for example : if you have a 320*320 image and you are going to show it as a 100*100 image, so resize it with any photo editor before you use it
You asked about optimizing by reducing the color depth.
JPEG images are normally defined with 24-bits color depth, which means that every pixel in the image requires 3 bytes. One optimization you can do is reduce the color depth to 8 BPP, so that each pixel only takes one byte.
A JPEG can be only saved as 24 BPP (Bits Per Pixel) or 8 BPP grayscale image. JPEG does not allow any other BPP values. If you want other BPP values, you need to use some other format such as PNG. But be warned that the quality of the colors will be strongly degraded.
Some tools that you can use to batch-change the color depth are:
You may want to use a software titled, XP Power Toys. You may download it from the following link:
There is a feature titled, Image Resizer.