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zoom.c
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/*
* lib/pandagl/src/zoom.c
*
* Copyright (c) 2023-2025, Liu Chao <[email protected]> All rights reserved.
*
* SPDX-License-Identifier: MIT
*
* This file is part of LCUI, distributed under the MIT License found in the
* LICENSE.TXT file in the root directory of this source tree.
*/
#include <pandagl.h>
static uint8_t canvas_bilinear_resampling_core(uint8_t a, uint8_t b, uint8_t c,
uint8_t d, float dx, float dy)
{
return (uint8_t)(a * (1 - dx) * (1 - dy) + b * (dx) * (1 - dy) +
c * (dy) * (1 - dx) + d * (dx * dy));
}
int pd_canvas_zoom(const pd_canvas_t *canvas, pd_canvas_t *buff,
bool keep_scale, int width, int height)
{
pd_rect_t rect;
int x, y, src_x, src_y;
double scale_x = 0.0, scale_y = 0.0;
if (!pd_canvas_is_valid(canvas) || (width <= 0 && height <= 0)) {
return -1;
}
/* 获取引用的有效区域，以及指向引用的对象的指针 */
pd_canvas_get_quote_rect(canvas, &rect);
canvas = pd_canvas_get_quote_source_readonly(canvas);
if (width > 0) {
scale_x = 1.0 * rect.width / width;
}
if (height > 0) {
scale_y = 1.0 * rect.height / height;
}
if (width <= 0) {
scale_x = scale_y;
width = (int)(0.5 + 1.0 * canvas->width / scale_x);
}
if (height <= 0) {
scale_y = scale_x;
height = (int)(0.5 + 1.0 * canvas->height / scale_y);
}
/* 如果保持宽高比 */
if (keep_scale) {
if (scale_x < scale_y) {
scale_y = scale_x;
} else {
scale_x = scale_y;
}
}
buff->color_type = canvas->color_type;
if (pd_canvas_create(buff, width, height) < 0) {
return -2;
}
if (canvas->color_type == PD_COLOR_TYPE_ARGB) {
pd_color_t *px_src, *px_des, *px_row_src;
for (y = 0; y < height; ++y) {
src_y = (int)(y * scale_y);
px_row_src = canvas->argb;
px_row_src += (src_y + rect.y) * canvas->width + rect.x;
px_des = buff->argb + y * width;
for (x = 0; x < width; ++x) {
src_x = (int)(x * scale_x);
px_src = px_row_src + src_x;
*px_des++ = *px_src;
}
}
} else {
uint8_t *byte_src, *byte_des, *byte_row_src;
for (y = 0; y < height; ++y) {
byte_row_src = pd_canvas_pixel_at(
canvas, rect.x, (int)(y * scale_y) + rect.y);
byte_des = pd_canvas_pixel_at(buff, 0, y);
for (x = 0; x < width; ++x) {
src_x = (int)(x * scale_x);
src_x *= canvas->bytes_per_pixel;
byte_src = byte_row_src + src_x;
*byte_des++ = *byte_src++;
*byte_des++ = *byte_src++;
*byte_des++ = *byte_src;
}
}
}
return 0;
}
int pd_canvas_zoom_bilinear(const pd_canvas_t *canvas, pd_canvas_t *buff,
bool keep_scale, int width, int height)
{
pd_rect_t rect;
pd_color_t a, b, c, d, t_color;
int x, y, i, j;
float x_diff, y_diff;
double scale_x = 0.0, scale_y = 0.0;
if (canvas->color_type != PD_COLOR_TYPE_RGB &&
canvas->color_type != PD_COLOR_TYPE_ARGB) {
/* fall back to nearest scaling */
logger_debug("[canvas] unable to perform bilinear scaling, "
"fallback...\n");
return pd_canvas_zoom(canvas, buff, keep_scale, width, height);
}
if (!pd_canvas_is_valid(canvas) || (width <= 0 && height <= 0)) {
return -1;
}
/* 获取引用的有效区域，以及指向引用的对象的指针 */
pd_canvas_get_quote_rect(canvas, &rect);
canvas = pd_canvas_get_quote_source_readonly(canvas);
if (width > 0) {
scale_x = 1.0 * rect.width / width;
}
if (height > 0) {
scale_y = 1.0 * rect.height / height;
}
if (width <= 0) {
scale_x = scale_y;
width = (int)(0.5 + 1.0 * canvas->width / scale_x);
}
if (height <= 0) {
scale_y = scale_x;
height = (int)(0.5 + 1.0 * canvas->height / scale_y);
}
/* 如果保持宽高比 */
if (keep_scale) {
if (scale_x < scale_y) {
scale_y = scale_x;
} else {
scale_x = scale_y;
}
}
buff->color_type = canvas->color_type;
if (pd_canvas_create(buff, width, height) < 0) {
return -2;
}
for (i = 0; i < height; i++) {
for (j = 0; j < width; j++) {
/*
* Qmn = (m, n).
* Qxy1 = (x2 - x) / (x2 - x1) * Q11 + (x - x1) / (x2
* - x1) * Q21
* Qxy2 = (x2 - x) / (x2 - x1) * Q12 + (x - x1) / (x2
* - x1) * Q22
* Qxy = (y2 - y) / (y2 - y1) * Qxy1 + (y - y1) / (y2 -
* y1) * Qxy2
*/
x = (int)(scale_x * j);
y = (int)(scale_y * i);
x_diff = (float)((scale_x * j) - x);
y_diff = (float)((scale_y * i) - y);
a = pd_canvas_get_pixel(canvas, x + rect.x + 0,
y + rect.y + 0);
b = pd_canvas_get_pixel(canvas, x + rect.x + 1,
y + rect.y + 0);
c = pd_canvas_get_pixel(canvas, x + rect.x + 0,
y + rect.y + 1);
d = pd_canvas_get_pixel(canvas, x + rect.x + 1,
y + rect.y + 1);
t_color.b = canvas_bilinear_resampling_core(
a.b, b.b, c.b, d.b, x_diff, y_diff);
t_color.g = canvas_bilinear_resampling_core(
a.g, b.g, c.g, d.g, x_diff, y_diff);
t_color.r = canvas_bilinear_resampling_core(
a.r, b.r, c.r, d.r, x_diff, y_diff);
t_color.a = canvas_bilinear_resampling_core(
a.a, b.a, c.a, d.a, x_diff, y_diff);
pd_canvas_set_pixel(buff, j, i, t_color);
}
}
return 0;
}