Rendering semi-transparent user interface elements

1. A computer-implemented method comprising:

increasing an intensity of a visual effect to be applied to a user interface element to be rendered over a background area based on a characteristic feature of the background area, the characteristic feature of the background area being based on color values for a sample of pixels from the background area, wherein the characteristic feature of the background area comprises brightness, and wherein the characteristic feature is distinct from the visual effect; and

rendering the user interface element based on the increased intensity of the visual effect.

2. The method of claim 1 , further comprising:

sampling pixels from the background area; and

determining a value of the characteristic feature of the background area based on the sampled pixels.

3. The method of claim 2 , wherein the characteristic feature of the background area further comprises one or more of:

an average color of the background area;

a histogram describing color frequencies in the background area; or

gradients describing color complexity of the background area.

4. The method of claim 1 , wherein the visual effect is opacity.

5. The method of claim 1 , wherein increasing the intensity of the visual effect comprises:

using a function to determine the intensity of the visual effect based on a determined value of the characteristic feature.

6. The method of claim 5 , further comprising:

deriving the function from a plurality of user-specified empirical data samples.

7. A system, comprising:

memory;

one or more processors; and

instructions stored in the memory and configured for execution by the one or more processors, the instructions comprising instructions that when executed cause the one or more processors to:

increase an intensity of a visual effect to be applied to a user interface element to be rendered over a background area based on a characteristic feature of the background area, the characteristic feature of the background area being based on color values for a sample of pixels from the background area, wherein the characteristic feature of the background area comprises brightness, and wherein the characteristic feature is distinct from the visual effect; and

render the user interface element based on the increased intensity of the visual effect.

8. A non-transitory computer-readable medium, on which are stored instructions, comprising instructions that when executed cause a data processing apparatus to:

increase an intensity of a visual effect to be applied to a user interface element to be rendered over a background area based on a characteristic feature of the background area, the characteristic feature of the background area being based on color values for a sample of pixels from the background area, wherein the characteristic feature of the background area comprises brightness, and wherein the characteristic feature is distinct from the visual effect; and

render the user interface element based on the increased intensity of the visual effect.

9. The computer-readable medium of claim 8 , wherein the instructions further comprise instructions that when executed cause the data processing apparatus to:

sample pixels from the background area; and

determine a value of the characteristic feature of the background area based on the sampled pixels.

10. The computer-readable medium of claim 9 , wherein the characteristic feature of the background area further comprises one or more of:

an average color of the background area;

a histogram describing color frequencies in the background area; or

gradients describing color complexity of the background area.

11. The computer-readable medium of claim 8 , wherein the visual effect is opacity.

12. The computer-readable medium of claim 8 , wherein the instructions that when executed cause the data processing apparatus to increase the intensity of the visual effect comprise instructions that when executed cause the data processing apparatus to:

use a function to determine the intensity of the visual effect based on a determined value of the characteristic feature.

13. The computer-readable medium of claim 12 , wherein the instruction stored thereon further comprise instructions that when executed cause the data processing apparatus to:

derive the function from a plurality of user-specified empirical data samples.

14. A computer-implemented method, comprising:

presenting a plurality of backgrounds, each of the backgrounds having a respective value for a characteristic feature;

for each of the presented backgrounds:

presenting a user interface element with the presented background; and

receiving user input adjusting an opacity value of the user interface element,

wherein the user input may increase or decrease the opacity value; and

deriving an opacity curve for the plurality of backgrounds using the respective opacity values and the respective characteristic feature values, wherein the opacity values are distinct from the characteristic feature values.

15. The method of claim 14 , further comprising, for each of the presented backgrounds, updating the presented user interface element to reflect the adjusted opacity value.

16. The method of claim 14 , wherein the characteristic feature is brightness.

17. The method of claim 14 , wherein presenting a user interface element with the respective presented background comprises presenting the user interface element with a predetermined opacity value.

18. A computer-implemented method, comprising:

identifying a background area of a graphical user interface over which a user interface element is to be rendered;

sampling pixels within the background area;

using the sampled pixels to determine a brightness value of the background area over which the user interface element is to be rendered, wherein the brightness value is determined based on color values of each of the sampled pixels;

increasing an opacity value of the user interface element based on the brightness value; and

rendering the user interface element over the background area of the graphical user interface based on the increased opacity value.