Image-processing apparatus and method
View Patent ↗A bit stream is decoded to generate first quantized DCT-coefficients. The first quantized DCT-coefficients are inversely quantized using a first quantization table, thereby generating DCT-coefficients. The resulting DCT-coefficients are quantized using a second quantization table, thereby generating second quantized DCT-coefficients. Elements in the second quantization table are smaller in value than those in the first quantization table. Predetermined additional information is embedded into the second quantized DCT-coefficients. The second quantized DCT-coefficients having the additional information embedded therein are encoded to produce a bit stream having the additional information embedded therein. The second quantization table is set to be smaller in value than the first quantization table.
1. An image-processing apparatus comprising:
a first quantization table;
a second quantization table different from said first quantization table;
an inverse quantization unit operable to inversely quantize first quantized data using said first quantization table, thereby generating frequency image data;
a quantization unit operable to quantize the frequency image data using said second quantization table, thereby generating second quantized data; and
an information-embedding unit operable to embed additional information into the second quantized data,
wherein each of said first and second quantization tables comprises elements at which the additional information is to be embedded, and wherein the elements in said second quantization table are smaller in value than the elements in said first quantization table.
2. An image-processing apparatus as defined in claim 1 , further comprising:
a decoding unit operable to decode compressed data, thereby generating the first quantized data; and
an encoding unit operable to encode the second quantized data having the additional information embedded therein by said information-embedding unit, thereby generating compressed data.
3. An image-processing apparatus as defined in claim 1 , wherein said information-embedding unit embeds the additional information in such a manner as to render a post-embedded value closer to “0”(zero) than a pre-embedded value.
4. An image-processing apparatus as defined in claim 1 , further comprising:
a table control unit operable to control values in said second quantization table based on values in said first quantization table.
5. An image-processing apparatus as defined in claim 1 , wherein the elements at which the additional information is to be embedded are determined along a zigzag-scanning path that begins at a direct-current component.
6. An image-processing method comprising:
inversely quantizing, using an inverse quantization unit, first quantized data using a first quantization table, thereby generating frequency image data;
quantizing, using a quantization unit, the frequency image data using a second quantization table different from the first quantization table, thereby generating second quantized data; and
embedding, using an information-embedding unit, additional information into the second quantized data,
wherein each of the first and second quantization tables comprises elements at which the additional information is to be embedded, and wherein the elements in the second quantization table are smaller in value than the elements in the first quantization table.
7. A computer readable storage medium having an image-processing program recorded therein in a computer readable manner, said image-processing program causing a computer to execute a method comprising:
inversely quantizing, using an inverse quantization unit, first quantized data using a first quantization table, thereby generating frequency image data;
quantizing, using a Quantization unit, the frequency image data using a second quantization table different from the first quantization table, thereby generating second quantized data; and
embedding, using an information-embedding unit, additional information into the second quantized data,
wherein each of the first and second quantization tables comprises elements at which the additional information is to be embedded, and wherein the elements in the second quantization table are smaller in value than the elements in the first quantization table.