diff options
Diffstat (limited to 'png/pngrtran.c')
| -rw-r--r-- | png/pngrtran.c | 346 |
1 files changed, 215 insertions, 131 deletions
diff --git a/png/pngrtran.c b/png/pngrtran.c index 1526123e0..1809db704 100644 --- a/png/pngrtran.c +++ b/png/pngrtran.c @@ -1,7 +1,6 @@ - /* pngrtran.c - transforms the data in a row for PNG readers * - * Copyright (c) 2018-2024 Cosmin Truta + * Copyright (c) 2018-2025 Cosmin Truta * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson * Copyright (c) 1996-1997 Andreas Dilger * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. @@ -29,6 +28,12 @@ # endif #endif +#ifdef PNG_RISCV_RVV_IMPLEMENTATION +# if PNG_RISCV_RVV_IMPLEMENTATION == 1 +# define PNG_RISCV_RVV_INTRINSICS_AVAILABLE +# endif +#endif + #ifdef PNG_READ_SUPPORTED /* Set the action on getting a CRC error for an ancillary or critical chunk. */ @@ -219,9 +224,59 @@ png_set_strip_alpha(png_structrp png_ptr) #endif #if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED) +/* PNGv3 conformance: this private API exists to resolve the now mandatory error + * resolution when multiple conflicting sources of gamma or colour space + * information are available. + * + * Terminology (assuming power law, "gamma", encodings): + * "screen" gamma: a power law imposed by the output device when digital + * samples are converted to visible light output. The EOTF - volage to + * luminance on output. + * + * "file" gamma: a power law used to encode luminance levels from the input + * data (the scene or the mastering display system) into digital voltages. + * The OETF - luminance to voltage on input. + * + * gamma "correction": a power law matching the **inverse** of the overall + * transfer function from input luminance levels to output levels. The + * **inverse** of the OOTF; the correction "corrects" for the OOTF by aiming + * to make the overall OOTF (including the correction) linear. + * + * It is important to understand this terminology because the defined terms are + * scattered throughout the libpng code and it is very easy to end up with the + * inverse of the power law required. + * + * Variable and struct::member names: + * file_gamma OETF how the PNG data was encoded + * + * screen_gamma EOTF how the screen will decode digital levels + * + * -- not used -- OOTF the net effect OETF x EOTF + * gamma_correction the inverse of OOTF to make the result linear + * + * All versions of libpng require a call to "png_set_gamma" to establish the + * "screen" gamma, the power law representing the EOTF. png_set_gamma may also + * set or default the "file" gamma; the OETF. gamma_correction is calculated + * internally. + * + * The earliest libpng versions required file_gamma to be supplied to set_gamma. + * Later versions started allowing png_set_gamma and, later, png_set_alpha_mode, + * to cause defaulting from the file data. + * + * PNGv3 mandated a particular form for this defaulting, one that is compatible + * with what libpng did except that if libpng detected inconsistencies it marked + * all the chunks as "invalid". PNGv3 effectively invalidates this prior code. + * + * Behaviour implemented below: + * translate_gamma_flags(gamma, is_screen) + * The libpng-1.6 API for the gamma parameters to libpng APIs + * (png_set_gamma and png_set_alpha_mode at present). This allows the + * 'gamma' value to be passed as a png_fixed_point number or as one of a + * set of integral values for specific "well known" examples of transfer + * functions. This is compatible with PNGv3. + */ static png_fixed_point -translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma, - int is_screen) +translate_gamma_flags(png_fixed_point output_gamma, int is_screen) { /* Check for flag values. The main reason for having the old Mac value as a * flag is that it is pretty near impossible to work out what the correct @@ -231,14 +286,6 @@ translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma, if (output_gamma == PNG_DEFAULT_sRGB || output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB) { - /* If there is no sRGB support this just sets the gamma to the standard - * sRGB value. (This is a side effect of using this function!) - */ -# ifdef PNG_READ_sRGB_SUPPORTED - png_ptr->flags |= PNG_FLAG_ASSUME_sRGB; -# else - PNG_UNUSED(png_ptr) -# endif if (is_screen != 0) output_gamma = PNG_GAMMA_sRGB; else @@ -280,6 +327,33 @@ convert_gamma_value(png_structrp png_ptr, double output_gamma) return (png_fixed_point)output_gamma; } # endif + +static int +unsupported_gamma(png_structrp png_ptr, png_fixed_point gamma, int warn) +{ + /* Validate a gamma value to ensure it is in a reasonable range. The value + * is expected to be 1 or greater, but this range test allows for some + * viewing correction values. The intent is to weed out the API users + * who might use the inverse of the gamma value accidentally! + * + * 1.6.47: apply the test in png_set_gamma as well but only warn and return + * false if it fires. + * + * TODO: 1.8: make this an app_error in png_set_gamma as well. + */ + if (gamma < PNG_LIB_GAMMA_MIN || gamma > PNG_LIB_GAMMA_MAX) + { +# define msg "gamma out of supported range" + if (warn) + png_app_warning(png_ptr, msg); + else + png_app_error(png_ptr, msg); + return 1; +# undef msg + } + + return 0; +} #endif /* READ_ALPHA_MODE || READ_GAMMA */ #ifdef PNG_READ_ALPHA_MODE_SUPPORTED @@ -287,31 +361,29 @@ void PNGFAPI png_set_alpha_mode_fixed(png_structrp png_ptr, int mode, png_fixed_point output_gamma) { - int compose = 0; png_fixed_point file_gamma; + int compose = 0; png_debug(1, "in png_set_alpha_mode_fixed"); if (png_rtran_ok(png_ptr, 0) == 0) return; - output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/); - - /* Validate the value to ensure it is in a reasonable range. The value - * is expected to be 1 or greater, but this range test allows for some - * viewing correction values. The intent is to weed out the API users - * who might use the inverse of the gamma value accidentally! - * - * In libpng 1.6.0, we changed from 0.07..3 to 0.01..100, to accommodate - * the optimal 16-bit gamma of 36 and its reciprocal. - */ - if (output_gamma < 1000 || output_gamma > 10000000) - png_error(png_ptr, "output gamma out of expected range"); + output_gamma = translate_gamma_flags(output_gamma, 1/*screen*/); + if (unsupported_gamma(png_ptr, output_gamma, 0/*error*/)) + return; /* The default file gamma is the inverse of the output gamma; the output - * gamma may be changed below so get the file value first: + * gamma may be changed below so get the file value first. The default_gamma + * is set here and from the simplified API (which uses a different algorithm) + * so don't overwrite a set value: */ - file_gamma = png_reciprocal(output_gamma); + file_gamma = png_ptr->default_gamma; + if (file_gamma == 0) + { + file_gamma = png_reciprocal(output_gamma); + png_ptr->default_gamma = file_gamma; + } /* There are really 8 possibilities here, composed of any combination * of: @@ -362,17 +434,7 @@ png_set_alpha_mode_fixed(png_structrp png_ptr, int mode, png_error(png_ptr, "invalid alpha mode"); } - /* Only set the default gamma if the file gamma has not been set (this has - * the side effect that the gamma in a second call to png_set_alpha_mode will - * be ignored.) - */ - if (png_ptr->colorspace.gamma == 0) - { - png_ptr->colorspace.gamma = file_gamma; - png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA; - } - - /* But always set the output gamma: */ + /* Set the screen gamma values: */ png_ptr->screen_gamma = output_gamma; /* Finally, if pre-multiplying, set the background fields to achieve the @@ -382,7 +444,7 @@ png_set_alpha_mode_fixed(png_structrp png_ptr, int mode, { /* And obtain alpha pre-multiplication by composing on black: */ memset(&png_ptr->background, 0, (sizeof png_ptr->background)); - png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */ + png_ptr->background_gamma = file_gamma; /* just in case */ png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE; png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND; @@ -820,8 +882,8 @@ png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma, return; /* New in libpng-1.5.4 - reserve particular negative values as flags. */ - scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/); - file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/); + scrn_gamma = translate_gamma_flags(scrn_gamma, 1/*screen*/); + file_gamma = translate_gamma_flags(file_gamma, 0/*file*/); /* Checking the gamma values for being >0 was added in 1.5.4 along with the * premultiplied alpha support; this actually hides an undocumented feature @@ -835,17 +897,19 @@ png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma, * libpng-1.6.0. */ if (file_gamma <= 0) - png_error(png_ptr, "invalid file gamma in png_set_gamma"); - + png_app_error(png_ptr, "invalid file gamma in png_set_gamma"); if (scrn_gamma <= 0) - png_error(png_ptr, "invalid screen gamma in png_set_gamma"); + png_app_error(png_ptr, "invalid screen gamma in png_set_gamma"); + + if (unsupported_gamma(png_ptr, file_gamma, 1/*warn*/) || + unsupported_gamma(png_ptr, scrn_gamma, 1/*warn*/)) + return; - /* Set the gamma values unconditionally - this overrides the value in the PNG - * file if a gAMA chunk was present. png_set_alpha_mode provides a - * different, easier, way to default the file gamma. + /* 1.6.47: png_struct::file_gamma and png_struct::screen_gamma are now only + * written by this API. This removes dependencies on the order of API calls + * and allows the complex gamma checks to be delayed until needed. */ - png_ptr->colorspace.gamma = file_gamma; - png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA; + png_ptr->file_gamma = file_gamma; png_ptr->screen_gamma = scrn_gamma; } @@ -1023,26 +1087,9 @@ png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action, png_ptr->rgb_to_gray_coefficients_set = 1; } - else - { - if (red >= 0 && green >= 0) - png_app_warning(png_ptr, - "ignoring out of range rgb_to_gray coefficients"); - - /* Use the defaults, from the cHRM chunk if set, else the historical - * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See - * png_do_rgb_to_gray for more discussion of the values. In this case - * the coefficients are not marked as 'set' and are not overwritten if - * something has already provided a default. - */ - if (png_ptr->rgb_to_gray_red_coeff == 0 && - png_ptr->rgb_to_gray_green_coeff == 0) - { - png_ptr->rgb_to_gray_red_coeff = 6968; - png_ptr->rgb_to_gray_green_coeff = 23434; - /* png_ptr->rgb_to_gray_blue_coeff = 2366; */ - } - } + else if (red >= 0 && green >= 0) + png_app_warning(png_ptr, + "ignoring out of range rgb_to_gray coefficients"); } } @@ -1283,6 +1330,80 @@ png_init_rgb_transformations(png_structrp png_ptr) #endif /* READ_EXPAND && READ_BACKGROUND */ } +#ifdef PNG_READ_GAMMA_SUPPORTED +png_fixed_point /* PRIVATE */ +png_resolve_file_gamma(png_const_structrp png_ptr) +{ + png_fixed_point file_gamma; + + /* The file gamma is determined by these precedence rules, in this order + * (i.e. use the first value found): + * + * png_set_gamma; png_struct::file_gammma if not zero, then: + * png_struct::chunk_gamma if not 0 (determined the PNGv3 rules), then: + * png_set_gamma; 1/png_struct::screen_gamma if not zero + * + * 0 (i.e. do no gamma handling) + */ + file_gamma = png_ptr->file_gamma; + if (file_gamma != 0) + return file_gamma; + + file_gamma = png_ptr->chunk_gamma; + if (file_gamma != 0) + return file_gamma; + + file_gamma = png_ptr->default_gamma; + if (file_gamma != 0) + return file_gamma; + + /* If png_reciprocal oveflows it returns 0 which indicates to the caller that + * there is no usable file gamma. (The checks added to png_set_gamma and + * png_set_alpha_mode should prevent a screen_gamma which would overflow.) + */ + if (png_ptr->screen_gamma != 0) + file_gamma = png_reciprocal(png_ptr->screen_gamma); + + return file_gamma; +} + +static int +png_init_gamma_values(png_structrp png_ptr) +{ + /* The following temporary indicates if overall gamma correction is + * required. + */ + int gamma_correction = 0; + png_fixed_point file_gamma, screen_gamma; + + /* Resolve the file_gamma. See above: if png_ptr::screen_gamma is set + * file_gamma will always be set here: + */ + file_gamma = png_resolve_file_gamma(png_ptr); + screen_gamma = png_ptr->screen_gamma; + + if (file_gamma > 0) /* file has been set */ + { + if (screen_gamma > 0) /* screen set too */ + gamma_correction = png_gamma_threshold(file_gamma, screen_gamma); + + else + /* Assume the output matches the input; a long time default behavior + * of libpng, although the standard has nothing to say about this. + */ + screen_gamma = png_reciprocal(file_gamma); + } + + else /* both unset, prevent corrections: */ + file_gamma = screen_gamma = PNG_FP_1; + + png_ptr->file_gamma = file_gamma; + png_ptr->screen_gamma = screen_gamma; + return gamma_correction; + +} +#endif /* READ_GAMMA */ + void /* PRIVATE */ png_init_read_transformations(png_structrp png_ptr) { @@ -1302,59 +1423,22 @@ png_init_read_transformations(png_structrp png_ptr) * the test needs to be performed later - here. In addition prior to 1.5.4 * the tests were repeated for the PALETTE color type here - this is no * longer necessary (and doesn't seem to have been necessary before.) + * + * PNGv3: the new mandatory precedence/priority rules for colour space chunks + * are handled here (by calling the above function). + * + * Turn the gamma transformation on or off as appropriate. Notice that + * PNG_GAMMA just refers to the file->screen correction. Alpha composition + * may independently cause gamma correction because it needs linear data + * (e.g. if the file has a gAMA chunk but the screen gamma hasn't been + * specified.) In any case this flag may get turned off in the code + * immediately below if the transform can be handled outside the row loop. */ - { - /* The following temporary indicates if overall gamma correction is - * required. - */ - int gamma_correction = 0; - - if (png_ptr->colorspace.gamma != 0) /* has been set */ - { - if (png_ptr->screen_gamma != 0) /* screen set too */ - gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma, - png_ptr->screen_gamma); + if (png_init_gamma_values(png_ptr) != 0) + png_ptr->transformations |= PNG_GAMMA; - else - /* Assume the output matches the input; a long time default behavior - * of libpng, although the standard has nothing to say about this. - */ - png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma); - } - - else if (png_ptr->screen_gamma != 0) - /* The converse - assume the file matches the screen, note that this - * perhaps undesirable default can (from 1.5.4) be changed by calling - * png_set_alpha_mode (even if the alpha handling mode isn't required - * or isn't changed from the default.) - */ - png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma); - - else /* neither are set */ - /* Just in case the following prevents any processing - file and screen - * are both assumed to be linear and there is no way to introduce a - * third gamma value other than png_set_background with 'UNIQUE', and, - * prior to 1.5.4 - */ - png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1; - - /* We have a gamma value now. */ - png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA; - - /* Now turn the gamma transformation on or off as appropriate. Notice - * that PNG_GAMMA just refers to the file->screen correction. Alpha - * composition may independently cause gamma correction because it needs - * linear data (e.g. if the file has a gAMA chunk but the screen gamma - * hasn't been specified.) In any case this flag may get turned off in - * the code immediately below if the transform can be handled outside the - * row loop. - */ - if (gamma_correction != 0) - png_ptr->transformations |= PNG_GAMMA; - - else - png_ptr->transformations &= ~PNG_GAMMA; - } + else + png_ptr->transformations &= ~PNG_GAMMA; #endif /* Certain transformations have the effect of preventing other @@ -1426,7 +1510,7 @@ png_init_read_transformations(png_structrp png_ptr) * appropriately. */ if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0) - png_colorspace_set_rgb_coefficients(png_ptr); + png_set_rgb_coefficients(png_ptr); #endif #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED @@ -1569,10 +1653,10 @@ png_init_read_transformations(png_structrp png_ptr) */ if ((png_ptr->transformations & PNG_GAMMA) != 0 || ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0 && - (png_gamma_significant(png_ptr->colorspace.gamma) != 0 || + (png_gamma_significant(png_ptr->file_gamma) != 0 || png_gamma_significant(png_ptr->screen_gamma) != 0)) || ((png_ptr->transformations & PNG_COMPOSE) != 0 && - (png_gamma_significant(png_ptr->colorspace.gamma) != 0 || + (png_gamma_significant(png_ptr->file_gamma) != 0 || png_gamma_significant(png_ptr->screen_gamma) != 0 # ifdef PNG_READ_BACKGROUND_SUPPORTED || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE && @@ -1628,8 +1712,8 @@ png_init_read_transformations(png_structrp png_ptr) break; case PNG_BACKGROUND_GAMMA_FILE: - g = png_reciprocal(png_ptr->colorspace.gamma); - gs = png_reciprocal2(png_ptr->colorspace.gamma, + g = png_reciprocal(png_ptr->file_gamma); + gs = png_reciprocal2(png_ptr->file_gamma, png_ptr->screen_gamma); break; @@ -1737,8 +1821,8 @@ png_init_read_transformations(png_structrp png_ptr) break; case PNG_BACKGROUND_GAMMA_FILE: - g = png_reciprocal(png_ptr->colorspace.gamma); - gs = png_reciprocal2(png_ptr->colorspace.gamma, + g = png_reciprocal(png_ptr->file_gamma); + gs = png_reciprocal2(png_ptr->file_gamma, png_ptr->screen_gamma); break; @@ -1988,11 +2072,11 @@ png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr) * been called before this from png_read_update_info->png_read_start_row * sometimes does the gamma transform and cancels the flag. * - * TODO: this looks wrong; the info_ptr should end up with a gamma equal to - * the screen_gamma value. The following probably results in weirdness if - * the info_ptr is used by the app after the rows have been read. + * TODO: this is confusing. It only changes the result of png_get_gAMA and, + * yes, it does return the value that the transformed data effectively has + * but does any app really understand this? */ - info_ptr->colorspace.gamma = png_ptr->colorspace.gamma; + info_ptr->gamma = png_ptr->file_gamma; #endif if (info_ptr->bit_depth == 16) |