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APNG Specification: Difference between revisions
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clarify that disposal happens to the output buffer before rendering the next frame
Herbyderby (talk | contribs) m (editorial changes) |
Herbyderby (talk | contribs) (clarify that disposal happens to the output buffer before rendering the next frame) |
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`y_offset` + `height` <= `IHDR` height | `y_offset` + `height` <= `IHDR` height | ||
The `delay_num` and `delay_den` parameters together specify a fraction indicating the delay after the current frame, in seconds. If the denominator is 0, it is to be treated as if it were 100 (that is, `delay_num` then specifies 1/100ths of a second). If the the value of the numerator is 0 the decoder should render the next frame as quickly as possible, though viewers may impose a reasonable lower bound on the delay. | The `delay_num` and `delay_den` parameters together specify a fraction indicating the delay after displaying the current frame, in seconds. If the denominator is 0, it is to be treated as if it were 100 (that is, `delay_num` then specifies 1/100ths of a second). If the the value of the numerator is 0 the decoder should render the next frame as quickly as possible, though viewers may impose a reasonable lower bound on the delay. | ||
`dispose_op` specifies how the output buffer should be changed at the end of the delay (before rendering the next frame). | |||
Valid values for `dispose_op` are: | Valid values for `dispose_op` are: | ||
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2 APNG_DISPOSE_OP_PREVIOUS | 2 APNG_DISPOSE_OP_PREVIOUS | ||
* APNG_DISPOSE_OP_NONE: no disposal is done on this frame before rendering the next; | * APNG_DISPOSE_OP_NONE: no disposal is done on this frame before rendering the next; the contents of the output buffer are left as is. | ||
* APNG_DISPOSE_OP_BACKGROUND: the frame's region of the output buffer is to be cleared to fully transparent black. | * APNG_DISPOSE_OP_BACKGROUND: the frame's region of the output buffer is to be cleared to fully transparent black before rendering the next frame. | ||
* APNG_DISPOSE_OP_PREVIOUS: the frame's region of the output buffer is to be reverted to the previous contents. | * APNG_DISPOSE_OP_PREVIOUS: the frame's region of the output buffer is to be reverted to the previous contents before rendering the next frame. | ||
`blend_op` specifies whether the frame is to be alpha blended into the current output buffer content, or whether it should completely replace its region in the output buffer. | `blend_op` specifies whether the frame is to be alpha blended into the current output buffer content, or whether it should completely replace its region in the output buffer. | ||