This API provides an interface for generating, decoding, and transforming planar YUV and JPEG images in memory.

Macro Definition Documentation

@@ -694,7 +695,6 @@ Variables

Chrominance subsampling options.

When pixels are converted from RGB to YCbCr (see TJCS_YCbCr) or from CMYK to YCCK (see TJCS_YCCK) as part of the JPEG compression process, some of the Cb and Cr (chrominance) components can be discarded or averaged together to produce a smaller image with little perceptible loss of image clarity (the human eye is more sensitive to small changes in brightness than to small changes in color.) This is called "chrominance subsampling".

NOTE: Technically, the JPEG format uses the YCbCr colorspace, but per the convention of the digital video community, the TurboJPEG API uses "YUV" to refer to an image format consisting of Y, Cb, and Cr image planes.

Enumerator

Enumerator
TJSAMP_444	4:4:4 chrominance subsampling (no chrominance subsampling). @@ -714,11 +714,13 @@ Variables
TJSAMP_440	4:4:0 chrominance subsampling. - The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image. Note that 4:4:0 subsampling is not fully accelerated in libjpeg-turbo. + The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image. + Note 4:4:0 subsampling is not fully accelerated in libjpeg-turbo.
TJSAMP_411	4:1:1 chrominance subsampling. - The JPEG or YUV image will contain one chrominance component for every 4x1 block of pixels in the source image. JPEG images compressed with 4:1:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:1:1 is better able to reproduce sharp horizontal features. Note that 4:1:1 subsampling is not fully accelerated in libjpeg-turbo. + The JPEG or YUV image will contain one chrominance component for every 4x1 block of pixels in the source image. JPEG images compressed with 4:1:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:1:1 is better able to reproduce sharp horizontal features. + Note 4:1:1 subsampling is not fully accelerated in libjpeg-turbo.

TJSAMP_444

4:4:4 chrominance subsampling (no chrominance subsampling).

@@ -714,11 +714,13 @@ Variables

TJSAMP_440

4:4:0 chrominance subsampling.

The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image. Note that 4:4:0 subsampling is not fully accelerated in libjpeg-turbo.

The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image.

Note: 4:4:0 subsampling is not fully accelerated in libjpeg-turbo.

TJSAMP_411

4:1:1 chrominance subsampling.

The JPEG or YUV image will contain one chrominance component for every 4x1 block of pixels in the source image. JPEG images compressed with 4:1:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:1:1 is better able to reproduce sharp horizontal features. Note that 4:1:1 subsampling is not fully accelerated in libjpeg-turbo.

Note: 4:1:1 subsampling is not fully accelerated in libjpeg-turbo.

@@ -1068,7 +1070,7 @@ If you choose option 1, *jpegSize should be set to the size of your

Compress a YUV planar image into a JPEG image.

Note that, if the width or height of the YUV image is not an even multiple of the MCU block size (see tjMCUWidth and tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.

Note: If the width or height of the YUV image is not an even multiple of the MCU block size (see tjMCUWidth and tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.

Parameters

@@ -1166,8 +1168,7 @@ If you choose option 1, *jpegSize should be set to the size of your

Decode a YUV planar image into an RGB or grayscale image.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG decompression process. The Y, U (Cb), and V (Cr) image planes should be stored sequentially in the source buffer, and the size of each plane is determined by the width and height of the source image, as well as the specified padding and level of chrominance subsampling. If the chrominance components are subsampled along the horizontal dimension, then the width of the luminance plane should be padded to the nearest multiple of 2 in the input image (same goes for the height of the luminance plane, if the chrominance components are subsampled along the vertical dimension.)

Parameters

handle a handle to a TurboJPEG compressor or transformer instance

@@ -1404,8 +1405,8 @@ If you choose option 1, *jpegSize should be set to the size of your

Decompress a JPEG image to a YUV planar image.

This function performs JPEG decompression but leaves out the color conversion step, so a planar YUV image is generated instead of an RGB image. The structure of the planes in this image is the same as in the images generated by tjEncodeYUV3(). Note that, if the width or height of the JPEG image is not an even multiple of the MCU block size (see tjMCUWidth and tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.

Note: If the width or height of the JPEG image is not an even multiple of the MCU block size (see tjMCUWidth and tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.

Parameters

handle a handle to a TurboJPEG decompressor or transformer instance

@@ -1521,8 +1522,7 @@ If you choose option 1, *jpegSize should be set to the size of your

Encode an RGB or grayscale image into a YUV planar image.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG compression process. The Y, U (Cb), and V (Cr) image planes are stored sequentially into the destination buffer, and the size of each plane is determined by the width and height of the source image, as well as the specified padding and level of chrominance subsampling. If the chrominance components are subsampled along the horizontal dimension, then the width of the luminance plane is padded to the nearest multiple of 2 in the output image (same goes for the height of the luminance plane, if the chrominance components are subsampled along the vertical dimension.)

Parameters

handle a handle to a TurboJPEG decompressor or transformer instance

diff --git a/turbojpeg.h b/turbojpeg.h index 818ca6e..0c66341 100644 --- a/turbojpeg.h +++ b/turbojpeg.h @@ -42,6 +42,11 @@ * TurboJPEG API. This API provides an interface for generating, decoding, and * transforming planar YUV and JPEG images in memory. * + * @note Technically, the JPEG format uses the YCbCr colorspace (which is + * technically not a colorspace but a color transform), but per the convention + * of the digital video community, the TurboJPEG API uses "YUV" to refer to an + * image format consisting of Y, Cb, and Cr image planes. + * * @{ */ @@ -59,10 +64,6 @@ * to produce a smaller image with little perceptible loss of image clarity * (the human eye is more sensitive to small changes in brightness than to * small changes in color.) This is called "chrominance subsampling". - *

- * NOTE: Technically, the JPEG format uses the YCbCr colorspace, but per the - * convention of the digital video community, the TurboJPEG API uses "YUV" to - * refer to an image format consisting of Y, Cb, and Cr image planes. */ enum TJSAMP { @@ -89,7 +90,8 @@ enum TJSAMP /** * 4:4:0 chrominance subsampling. The JPEG or YUV image will contain one * chrominance component for every 1x2 block of pixels in the source image. - * Note that 4:4:0 subsampling is not fully accelerated in libjpeg-turbo. + * + * @note 4:4:0 subsampling is not fully accelerated in libjpeg-turbo. */ TJSAMP_440, /** @@ -99,8 +101,9 @@ enum TJSAMP * same size as those compressed with 4:2:0 subsampling, and in the * aggregate, both subsampling methods produce approximately the same * perceptual quality. However, 4:1:1 is better able to reproduce sharp - * horizontal features. Note that 4:1:1 subsampling is not fully accelerated - * in libjpeg-turbo. + * horizontal features. + * + * @note 4:1:1 subsampling is not fully accelerated in libjpeg-turbo. */ TJSAMP_411 }; @@ -636,10 +639,11 @@ DLLEXPORT int DLLCALL tjCompress2(tjhandle handle, unsigned char *srcBuf, /** - * Compress a YUV planar image into a JPEG image. Note that, if the width or - * height of the YUV image is not an even multiple of the MCU block size - * (see #tjMCUWidth and #tjMCUHeight), then an intermediate buffer copy will be - * performed within TurboJPEG. + * Compress a YUV planar image into a JPEG image. + * + * @note If the width or height of the YUV image is not an even multiple of the + * MCU block size (see #tjMCUWidth and #tjMCUHeight), then an intermediate + * buffer copy will be performed within TurboJPEG. * * @param handle a handle to a TurboJPEG compressor or transformer instance * @param srcBuf pointer to an image buffer containing a YUV planar image @@ -746,10 +750,6 @@ DLLEXPORT unsigned long DLLCALL tjBufSizeYUV2(int width, int pad, int height, * plane is padded to the nearest multiple of 2 in the output image (same goes * for the height of the luminance plane, if the chrominance components are * subsampled along the vertical dimension.) - *

- * NOTE: Technically, the JPEG format uses the YCbCr colorspace, but per the - * convention of the digital video community, the TurboJPEG API uses "YUV" to - * refer to an image format consisting of Y, Cb, and Cr image planes. * * @param handle a handle to a TurboJPEG compressor or transformer instance * @param srcBuf pointer to an image buffer containing RGB or grayscale pixels @@ -886,14 +886,11 @@ DLLEXPORT int DLLCALL tjDecompress2(tjhandle handle, * Decompress a JPEG image to a YUV planar image. This function performs JPEG * decompression but leaves out the color conversion step, so a planar YUV * image is generated instead of an RGB image. The structure of the planes in - * this image is the same as in the images generated by #tjEncodeYUV3(). Note - * that, if the width or height of the JPEG image is not an even multiple of + * this image is the same as in the images generated by #tjEncodeYUV3(). + * + * @note If the width or height of the JPEG image is not an even multiple of * the MCU block size (see #tjMCUWidth and #tjMCUHeight), then an intermediate * buffer copy will be performed within TurboJPEG. - *

- * NOTE: Technically, the JPEG format uses the YCbCr colorspace, but per the - * convention of the digital video community, the TurboJPEG API uses "YUV" to - * refer to an image format consisting of Y, Cb, and Cr image planes. * * @param handle a handle to a TurboJPEG decompressor or transformer instance * @param jpegBuf pointer to a buffer containing the JPEG image to decompress @@ -940,10 +937,6 @@ DLLEXPORT int DLLCALL tjDecompressToYUV2(tjhandle handle, * luminance plane should be padded to the nearest multiple of 2 in the input * image (same goes for the height of the luminance plane, if the chrominance * components are subsampled along the vertical dimension.) - *

- * NOTE: Technically, the JPEG format uses the YCbCr colorspace, but per the - * convention of the digital video community, the TurboJPEG API uses "YUV" to - * refer to an image format consisting of Y, Cb, and Cr image planes. * * @param handle a handle to a TurboJPEG decompressor or transformer instance * @param srcBuf pointer to an image buffer containing a YUV planar image to be

handle a handle to a TurboJPEG compressor or transformer instance

Detailed Description

Macro Definition Documentation