Abstract: Methods, systems, and computer programs for encoding images are described. In one aspect, quantized frequency domain vectors are sequentially generated from a sequence of blocks of the image. Each quantized frequency domain vector includes a set of quantized forward transform coefficients that are derived from a respective image block. For each successive quantized frequency domain vector, a current input capacity level of a buffer is determined and the quantized frequency domain vector is modified to increase compressibility when the current input capacity level is determined to be below a prescribed threshold. Modified and unmodified quantized frequency domain vectors are encoded into a sequence of encoded image blocks. The sequence of encoded image blocks is stored in the buffer.

Abstract: An adaptive image tone mapping curve based on perceptual preference guidelines is generated as a sigmoidal function, in which the sigmoidal function parameters (slope and shift) are determined by original image statistics. Tone curves generated for different images each have a smooth sigmoidal shape, so that the tone mapping process does not change the image histogram shape drastically. The sigmoidal function has the form: t ? ( x ) = 100 1 + exp ? ( - ? ? ( x / 100 - ? ) ) , where ? is the slope parameter and ? is the shift parameter. The input value x in the sigmoidal function varies in the range [0, 100], because the tone curve is generated on an L* scale, which has values from 0 to 100.

Abstract: An adaptive image tone mapping curve based on perceptual preference guidelines is generated as a sigmoidal function, in which the sigmoidal function parameters (slope and shift) are determined by original image statistics. Tone curves generated for different images each have a smooth sigmoidal shape, so that the tone mapping process does not change the image histogram shape drastically.

Abstract: A power supply circuit for an LED print head has a reference current source connected to a printer system reference voltage for providing a second reference voltage for an individual, integrated circuit chip. The reference current source is controlled by an operational amplifier, the output of which comprises the second reference voltage. A plurality of output driver FETs are biased by the reference voltage. Each output driver FET provides current to an associated LED responsive to a data signal. A plurality of control FETs are connected in parallel with each other and in series with each output driver FET for varying the LED output current responsive to programming data signals. A second group of control FETs is interposed in the feedback loop of the operational amplifier for varying the second reference voltage responsive to a different set of programming data signals.

Abstract: A circuit for controlling the energy delivered to a heater resistor of a thermal inkjet printhead. The circuit includes a decoder for receiving an address for the heater resistor in a multiplexed environment. When the heater resistor is addressed, the output of the decoder is level shifted through a pair of inverters and transmitted to the gate of a PMOS driver that delivers the energy to the heater resistor. The PMOS driver responds to the voltage level of the adjacent inverter output in setting the level of the driver output voltage that is applied to the resistor. Feedback circuitry in the form of an analog or digital comparator compares the driver output voltage against a reference voltage. The comparator's output signal is fed back through the level shifter as the inverter output that is applied to the gate of the PMOS driver.

Abstract: A power supply circuit for an LED print head has a reference current source connected to a printer system reference voltage for providing a second reference voltage for an individual, integrated circuit chip. A plurality of substantially similar field effect transistors have their gates connected to the chip reference voltage for providing substantially similar current to each of a plurality of light emitting diodes. The current is enabled to each such LED by the presence or absence of a data signal. A reference resistor in the reference current source permits adjustment so that each of a plurality of integrated circuit chips can provide substantially similar current to each of a plurality of LED dice, or adjust the current level, if required, to achieve similar light output from each LED.