Image Cropper JPEG re-
Loading an image into Image Cropper then saving it out again can potentially cause a loss of quality due to de-
This test was carried out by comparing Image Cropper to JpegCrops, a lossless Jpeg cropping program. Image Cropper is using the Lanczos resizing algorithm.
Magnified 240x160 pixel centre of the 1920x1080 cropped images
Left: Image Cropper Right: Jpegcrops lossless crop
The original image is 5184x3456 18MP jpeg best quality taken using a Canon 600D with a
This image was then cropped to 1920x1080 with no re-
Note: Only certain ratios (multiples of 16 pixels) can be cropped losslessly and 1920x1080 Full HD is not one of them for this original size, so the nearest was taken.
Original Image 5184x3456 pixels 7.5MB Magnified centre of the original image
Cropped to 1920x1080 by Image Cropper Cropped to approx 1920x1080 by JpegCrops
File size: 790KB File size: 798KB
Quality : 98 Quality: as original (Canon ‘large’)
This clearly demonstrates that for a high quality jpeg image using Image Cropper to de-
However, the situation changes significantly with low quality images.
The high quality original was saved using a jpeg quality of just 15 reducing the file size from 7.7MB to only 680KB. This was then cropped using Image Cropper and JpegCrops to 1920x1080.
Left: Original LOW quality image Right: Jpegcrops lossless 1920x1080 crop
File size: 60KB
Magnified 240x160 pixel centre. As you would expect the two are identical.
Left: Image Cropper saved at quality 85 Right: Image Cropper saved at quality 15
File size: 203KB File size: 87KB
Clearly with a high degree of compression in the original image further re-
For good quality Jpegs cropped and processed in Image Cropper there is little need to worry about quality loss if saved back with good quality.
If you need to work with highly compressed images AND retain a small file size a lossless cropper may be a better choice, but if you just wish to crop and compress good images such as for a web page Image Cropper will do a good job.
Another very extreme test. The 1920x1080 jpeg image was loaded into Image Cropper and saved back to a jpeg at quality 98. The copy just saved was then loaded in and saved again. This was then done 10 times -
This the the centre of the image after 10 generations, that is, 10 de-
Compare this with the first generation images above. The colour saturation has dropped very slightly but jpeg artifacts are no more apparent.
A quality of setting of 98 seems to maintain the original file size. At 99 it grew a little each time, 787KB to 899KB. At 97 it shrank a little from 787KB to 748KB.
Although this may be only low compression it is still a big saving over a bitmap which would be about 6MB.