Convert images to grayscale by setting the effect parameter to grayscale (e_grayscale in URLs). You can add further transformations in order to achieve the exact result you need.
Here's an original image for example:
https://res.cloudinary.com/demo/image/upload/happy_dog.jpgHere's how to apply the 'grayscale' effect:
https://res.cloudinary.com/demo/image/upload/e_grayscale/happy_dog.jpgYou can also apply the grayscale effect on overlay images. For example, here's Cloudinary's logo:
https://res.cloudinary.com/demo/image/upload/cloudinary_icon.pngopacity parameter to 50 (o_50 in URLs):
https://res.cloudinary.com/demo/image/upload/l_cloudinary_icon,e_grayscale,w_1500,o_50/happy_dog.jpgHere's a more advanced and interesting example of applying the grayscale effect on overlays. This time, we'll use the dog's image as a texture to the logo (Using the same technique as the recipe - Use images as text textures):
https://res.cloudinary.com/demo/image/upload/l_cloudinary_icon,fl_cutter/happy_dog.png
https://res.cloudinary.com/demo/image/upload/e_grayscale/l_cloudinary_icon,fl_cutter/happy_dog.png
https://res.cloudinary.com/demo/image/upload/e_grayscale/l_cloudinary_icon,fl_cutter.relative,w_0.7/u_happy_dog/happy_dog.jpgNote that you can use a similar practice to grayscale only certain parts of the image:
https://res.cloudinary.com/demo/image/upload/l_happy_dog,w_2082,h_500,c_crop,g_north,e_grayscale/g_north,fl_layer_apply/l_happy_dog,w_2082,h_500,c_crop,e_grayscale/fl_layer_apply/l_happy_dog,w_2082,h_500,c_crop,g_south,e_grayscale/g_south,fl_layer_apply/happy_dog.jpgHere's another example of using the gradient_fade effect (e_gradient in URLs) to create a smooth transition from grayscale to color:
https://res.cloudinary.com/demo/image/upload/e_gradient_fade,x_0.9/u_happy_dog,e_grayscale/happy_dog.jpg