QuickTime 4 Reference

Destination Color Limits

The deviceMinimum and deviceMaximum fields in a color component's gxTransferComponent structure define the allowable range of values for destination color in that component. Destination color values outside of the range cause no drawing to occur for that color. If deviceMaximum is less than deviceMinimum , the range allowed consists of values less than deviceMaximum or greater than deviceMinimum . Figure 53 shows the effect of deviceMinimum and deviceMaximum on drawing using blend mode.

Figure 53 The effect of destination color limits on drawing

Note in Figure 53 that, when deviceMinimum is less than deviceMaximum , only the letter "A" in the destination image is within the destination limits, so the source is blended with the destination image only within the limits of the "A" to create the result. Conversely, when deviceMaximum is less than deviceMinimum , the "A" is outside the destination limits, so it is the only part of the destination not blended with the source to create the result.